GitHub Copilot is an AI pair programmer providing real-time code suggestions and completions in the IDE. How it works: Analyzes context (current file, open files, comments, function names), predicts likely code continuations, suggestions appear inline or in panel. Powered by: OpenAI Codex variants, now GPT-4-based (Copilot X features). Features: Line completions, function generation, multi-line suggestions, chat interface (Copilot Chat), natural language to code. Integration: VS Code, JetBrains IDEs, Neovim, Visual Studio. Deep IDE integration for context awareness. Training data: GitHub public repositories (licensing controversies), refined through user feedback. Effectiveness: Studies show 30-50% faster task completion for applicable tasks. Most valuable for boilerplate, unfamiliar APIs, repetitive patterns. Pricing: Individual and business tiers, free for education/open source maintainers. Alternatives: Cody (Sourcegraph), Cursor, Amazon CodeWhisperer, Tabnine, Continue. Best practices: Use for acceleration not replacement, review suggestions, understand generated code. Widely adopted despite licensing debates.