Tech Vocabulary

Application Programming Interface. A contract defining how software components communicate. Specifies available operations, required inputs, and expected outputs. REST APIs use HTTP verbs (GET, POST, PATCH, DELETE) with JSON payloads. Enables systems to integrate without knowing each other's internals.

Modern JavaScript syntax for handling asynchronous operations. async marks a function as returning a Promise; await pauses execution until a Promise resolves. Cleaner than callback chains. Makes async code read like synchronous code. Essential for API calls, file operations, and any I/O.

Bourne Again Shell. The default command-line interpreter on Linux and macOS. Runs commands, scripts, and manages files. Windows uses PowerShell instead, but Git Bash brings Bash to Windows.

A data type with only two values: true or false. Named after mathematician George Boole. Used for conditions, flags, and logic. isActive, hasPermission, shouldRender are typical boolean variable names.

In Git, a parallel line of development. main is the default branch. Create a branch to work on a feature without affecting main code. Merge branches when work is complete. Enables multiple people to work simultaneously without conflicts.

Transforming source code into deployable output. Compiling TypeScript to JavaScript, bundling files, optimising assets. npm run build creates production-ready output. The build step catches errors before deployment.

Temporary storage for frequently accessed data to speed up retrieval. Instead of re-fetching from the database or API, check the cache first. Knowing when cached data is stale is notoriously hard.

Continuous Integration / Continuous Deployment. Automated pipelines that build, test, and deploy code. Push to GitHub, CI runs tests, CD deploys to production. Catches bugs before they reach users.

Command Line Interface. A text-based way to interact with software by typing commands. The opposite of GUI. Examples: git, npm, curl. Powerful for automation and scripting.

Cross-Origin Resource Sharing. A browser security feature controlling which domains can access resources. By default, browsers block requests from one domain to another. CORS headers explicitly permit cross-origin requests. Common pain point when frontend and API are on different domains.

Create, Read, Update, Delete. The four basic operations for persistent storage. Most applications are CRUD apps at their core. Maps to HTTP verbs: POST (create), GET (read), PATCH/PUT (update), DELETE (delete).

Command-line tool for transferring data via URLs. curl https://api.example.com fetches data. Add -X POST for POST requests, -H for headers, -d for body data. Essential for testing APIs without a browser.

Organised collection of data with systems to store, query, and manage it. Relational databases (PostgreSQL, MySQL) use tables with rows and columns, queried via SQL. Databases ensure persistence, handle concurrent access, and enforce constraints.

A comparison showing differences between two versions of text or code. Lines added show with +, removed with -. Git uses diffs to show changes between commits. Essential for code review.

Document Object Model. The browser's tree representation of an HTML page. JavaScript manipulates the DOM to update what users see. Each HTML element becomes a node in the tree.

Enumeration. A type that defines a fixed set of named values. Instead of magic strings like "active" or "done", you use Status.Active or Status.Done. Prevents typos, enables autocomplete, and makes valid values explicit.

Environment variables. Configuration values set outside your code. Stored in .env files or system settings. Keep secrets out of code: API keys, database URLs, feature flags. Never commit .env to Git.

Distributed version control system for tracking code changes. Every developer has the full history locally. Key concepts: commits (snapshots), branches (parallel lines of work), merges (combining branches). Essential for collaboration.

Cloud platform for hosting Git repositories. Adds collaboration features: pull requests (propose changes), issues (track bugs and tasks), actions (automated workflows), and code review. Free for public repos.

Graphical User Interface. A visual way to interact with software using windows, buttons, icons, and mouse clicks. The opposite of CLI. Web apps, desktop apps, and mobile apps are GUIs. Easier to learn but harder to automate.

HyperText Transfer Protocol. The foundation of web communication. Client sends request (method, URL, headers, body), server returns response (status code, headers, body). HTTPS adds encryption via TLS.

Internet of Things. Physical devices connected to the internet that collect and exchange data. Includes sensors, smart home devices, and industrial equipment. Typically low-power and always-on.

The language of the web. Runs in browsers (frontend) and servers (Node.js backend). Dynamic typing, event-driven. TypeScript adds static types on top. npm manages its packages.

JavaScript Object Notation. A lightweight text format for structured data. Human-readable and machine-parseable. Uses key-value pairs and arrays. The universal data exchange format for web APIs, config files, and storage.

JSON Web Token. A compact, self-contained token for securely transmitting information. Three parts: header, payload, signature. The payload contains claims like user ID and expiration. Common for API authentication.

Static analysis that checks code for errors, style issues, and suspicious patterns without running it. ESLint for JavaScript. Catches bugs early: unused variables, missing imports, inconsistent formatting.

Free, open-source Unix-like operating system. Powers most servers, cloud infrastructure, Android phones, and developer machines. Created by Linus Torvalds in 1991. WSL brings Linux to Windows.

Large Language Model. AI trained on massive text datasets to understand and generate language. GPT-4, Claude, and Gemini are LLMs. They predict likely next tokens based on context. Useful for coding, writing, analysis, and conversation.

Model Context Protocol. A standard for connecting LLMs to external tools and data sources. Servers expose tools (functions the LLM can call) and resources (data it can read). Think of it as plugins for LLMs.

Code that runs between receiving a request and sending a response. In web frameworks, middleware processes requests in a pipeline: authentication, logging, rate limiting. Each middleware can modify the request or pass to the next.

A versioned change to a database schema. Instead of manually altering tables, migrations define changes in code. They run in sequence, can be rolled back, and keep schema history.

React framework for production web applications. Created by Vercel. Adds routing, server-side rendering, API routes, and build optimisation on top of React. The standard choice for modern React apps.

Node Package Manager. JavaScript's package registry and CLI tool. Downloads libraries from npmjs.com into node_modules/. package.json lists dependencies. npm install adds packages, npm run executes scripts.

The actual data being transmitted, separate from metadata and headers. In an API request, the payload is the JSON body. In a JWT, the payload holds claims like user ID.

High-level programming language known for readable syntax and versatility. Dominant in data science, AI/ML, automation, and scripting. Great for quick scripts and prototyping. Huge ecosystem via pip.

JavaScript library for building user interfaces. Created by Facebook. Uses components (reusable UI pieces) and JSX (HTML-like syntax in JavaScript). Declarative: describe what the UI should look like, React handles updates.

Regular Expression. A pattern language for matching text. Powerful but cryptic. Used by grep, search-and-replace, and input validation. Worth learning basics; use tools to build complex patterns.

Representational State Transfer API. An architectural style for web services. Resources have URLs. HTTP verbs define actions: GET retrieves, POST creates, PATCH updates, DELETE removes. Stateless and widely adopted.

When code is actually executing. A runtime error means it crashed while running. Also refers to the environment that executes code: Node.js is a JavaScript runtime.

The structure definition for data. Database schema defines tables, columns, types, and relationships. Schema changes require migrations.

Cloud computing model where you don't manage servers. Code runs on-demand in response to events. You pay per execution, not for idle servers. Scales automatically.

Structured Query Language. The standard language for relational databases. SELECT retrieves data, INSERT adds, UPDATE modifies, DELETE removes. JOIN combines tables. Used by PostgreSQL, MySQL, SQLite.

Open-source database platform built on PostgreSQL. Provides a database, REST API, authentication, and real-time subscriptions out of the box. Access via client library or direct SQL.

Utility-first CSS framework. Instead of writing custom CSS, compose styles from pre-defined utility classes. Produces small CSS bundles by purging unused classes.

Transport Layer Security. The cryptographic protocol that secures internet communication. The "S" in HTTPS. Encrypts data in transit. Uses certificates to verify server identity.

A unit of text in LLM processing. Roughly a word or word fragment. LLMs have context limits measured in tokens. Also used in authentication: API tokens are secret keys that prove identity.

JavaScript with static types. You declare what type a variable is, and the compiler catches type errors before runtime. Developed by Microsoft. Compiles to plain JavaScript.

Universally Unique Identifier. A 128-bit label for uniquely identifying information. Format: 550e8400-e29b-41d4-a716-446655440000. Used as primary keys in databases. Generated randomly; collision probability is negligible.

Cloud platform for deploying frontend applications. Optimised for Next.js. Push to GitHub, Vercel auto-deploys. Provides preview URLs for branches and edge functions. Free tier for personal projects.

HTTP callback that notifies your system when something happens elsewhere. Instead of polling an API repeatedly, register a webhook URL and receive POST requests when events occur.

Windows Subsystem for Linux. Lets you run Linux commands on a Windows PC. Once installed, you open it like any other app and you're in a Linux terminal. Essential for developers on Windows who need Unix tools.