Glossary

Short, beginner-friendly definitions for terms that show up while learning to code.

📘 Code Quality

Refactoring: Restructuring code without changing its behavior. Not bug-fixing, not feature-adding — just making it easier to read and change.
Naming: How you name variables and functions. Clarity beats brevity. Good names eliminate the need for most comments.
Function: A named, reusable unit of code. Rule of thumb: do one thing, well. Long functions are hard to read and harder to test.
Clean Code: Code that doesn't confuse the next reader (often, future you). Named after the classic book by Robert C. Martin.

SOLID: Five letters spelling out core design principles. The foundation for code that lasts as it grows.
DRY: Don't Repeat Yourself. When you write the same logic three times, it's a sign to consolidate.
KISS: Keep It Simple, Stupid. "Clever code" and "simple code" are not the same thing.
Design Pattern: A standard solution for a common design problem. Don't memorize — recognize "oh, this situation".
Single Responsibility Principle: A class or function should have one reason to change. Code that does everything ends up doing nothing well.

N+1 Problem: When showing a list of "1 parent + N children" issues N+1 queries instead of one. Quietly slow at small scale, fatal at large.
Index: A data structure that speeds up reads. Like a book's back-of-the-book index. Not free — write speed pays the cost.
Normalization: Schema design discipline that removes duplicate data. Usually applied through 1st, 2nd, and 3rd normal forms.
Transaction: A way to make multiple writes succeed or fail together. Prevents partial states when something crashes mid-update.

API: Application Programming Interface — a doorway for one system to talk to another.
Endpoint: A specific URL within an API. Example: `/api/users` is the "users counter".
REST API: An API style that maps resources to URLs and actions to HTTP methods (GET/POST/PUT/DELETE).
Environment Variable (env): Configuration kept outside code. The home for API keys and DB passwords. A stray newline character will silently break it.
OAuth: Lets one service act on your behalf in another, without sharing your password. The plumbing behind "Sign in with GitHub".

Learn from code: Paste your code (or pick from GitHub), and AI walks you through it using concepts from classic CS books.
Learn from bugs: Paste an error message and AI explains the cause while pointing you to the relevant book chapter.
Crossbook: Compare how multiple books describe the same concept. The art of connecting books, made visible.
Level Diagnosis: A 15-question AI conversation that maps your current level by domain (code quality, architecture, DB, etc.).
Custom Curriculum: AI-generated learning path based on your goals and current level.

Once the terms feel familiar, try learning from your own code.