What is GitHub Copilot Chat and how does it differ from inline completions?

GitHub Copilot Chat is a conversational interface embedded in your IDE where you can ask questions, request refactors, explain code, or get help with errors in natural language. Inline completions are the grey ghost text that appears as you type code. Chat is better for complex requests ("refactor this class to use the strategy pattern") while inline is better for rapid autocomplete during normal coding flow.