Glossary

Short, plain-language explanations of the terms used in the course.

.env file: A file holding your project's settings and secrets (keys, passwords). It never goes into Git.
Absolute path: A full path starting from the root /, which means the same thing no matter where you are.
AI coding agent: A tool that reads your project, plans changes, and edits real files on your machine — not just a chat window that suggests code.
API: An agreed set of rules that lets one program talk to another.
Argument: What a command acts on — usually a file or folder name written after the command.
Branch: A parallel line of work in Git, so you can change things without touching the main version.
Claude Code: Anthropic's coding agent: it reads your project and writes or changes code from instructions in plain language.
CLAUDE.md: A file at the root of your project holding instructions for the agent: rules, commands, conventions. It gets read automatically.
CLI: Command-line interface — driving a program by typing commands instead of clicking.
Codex: OpenAI's coding agent, working in the same terminal-and-project shape as other agents.
Command: One instruction for the terminal, like ls or cd. You type it and press Enter.
Commit: A saved snapshot of your changes in Git, with a message saying what changed and why.
Context window: How much text the model can hold at once. When it fills up, the oldest material falls out.
Current directory: The folder you are standing in right now. pwd prints it.
Cursor: An editor with an AI agent built in — the same idea as a terminal agent, wrapped in an IDE.
Database: Organized storage you can search, add to, and update without losing track of anything.
Dependency: Someone else's package that your project needs to run. They are listed in package.json.
Deploy: Publishing your project so other people can reach it on the internet.
Diff: A side-by-side view of what changed: green lines were added, red lines were removed.
Directory: A container for files and other directories. "Folder" means the same thing.
Domain: A site's address on the internet, like example.com — what people type in the address bar.
Environment variable: A named value programs can read, like PATH or HOME.
Executable: A file you can run as a program. The +x permission is what makes it one.
Flag: A switch that changes how a command behaves, like the -a in "ls -a". Flags usually start with a dash.
Framework: A ready-made skeleton for applications: it handles the plumbing so you write the logic.
Gemini CLI: Google's coding agent for the terminal, built around very large context windows.
Git: Version control: it records the history of your code so you can see what changed and go back.
GitHub: A website that hosts Git repositories in the cloud and lets people work on them together.
Hallucination: When a model states something false with complete confidence — an API that does not exist, a function that was never written.
Home folder: Your personal folder, written as ~. Most work starts here.
Hooks: Scripts the agent runs automatically on events — before a commit, after a file changes.
HTTP: The protocol a browser uses to ask servers for pages and data.
JSON: A plain-text format for data, written as key-value pairs. Both people and programs can read it.
Linter: A tool that automatically flags mistakes and style problems in code, like ESLint.
localhost: Your own machine's address (127.0.0.1). A local dev server usually opens at localhost:3000.
Markdown: Formatting plain text with symbols: # for headings, * for lists. Files end in .md.
MCP: Model Context Protocol — the standard way an agent plugs into outside tools and data sources.
MVP: Minimum viable product — the smallest version that actually works and is worth showing.
Node.js: The runtime that lets JavaScript run outside a browser — on your machine or a server.
npm: The package manager for Node.js: it installs and updates the packages your project depends on.
Package: A ready-made piece of code you can install and use in your project.
Path: The address of a file or folder, like /home/user/notes.txt.
Permissions: Who may read, change, or run a file. chmod changes them — chmod +x makes a file runnable.
Pipe: The | character, which feeds one command's output straight into the next command.
Plan mode: A mode where the agent shows you the plan first and waits for approval — nothing changes until you say yes.
Process: A running program. The terminal waits for it to finish, or you stop it with Ctrl+C.
Prompt: What you ask the model. The more specific the prompt, the more useful the answer.
Redirect: Sending a command's output into a file: > overwrites the file, >> appends to it.
Refactor: Rewriting code so it reads better or runs cleaner, without changing what it does.
Relative path: A path read from the folder you are in right now, like ./projects or ../..
Repository: A project folder tracked by Git, together with its whole history.
Server: A program (or machine) that answers requests — handing back a web page, for instance.
Shell: The program inside the terminal that reads your commands and runs them — bash and zsh are the common ones.
Shell prompt: The short line of text before your cursor in the terminal, telling you who you are and where you are. Not the same thing as a prompt to a model.
Skill: A packaged set of instructions and tools that gives an agent a new ability on demand.
Slash command: A shortcut typed with a leading slash, like /help, that runs a predefined action.
SQL: The query language for databases: what to select, insert, or change.
Subagent: A helper the main agent hands part of a task to, working on it in its own separate context.
Terminal: A window where you type text commands and the computer runs them.
Token: A chunk of text — roughly a word or part of one. Models measure input and output length in tokens.
Vibe coding: Building software by describing what you want to an AI agent in plain language, then steering and reviewing what it writes.