What is GitHub Copilot's primary feature?

GitHub describes Copilot as "an AI coding assistant that helps you write code faster and with less effort", and the feature carrying most of that load is inline completion. In the editor, "Copilot offers coding suggestions as you type. Start typing in the editor, and Copilot provides dimmed ghost text suggestions at your current cursor location." You take one with a keystroke, or keep typing and it withdraws.

The dimming matters more than it sounds. The suggestion is a proposal you read and accept, not an edit that happens to you — which is why reviewing it is your job and not an optional extra. Copilot has grown well beyond this since, with chat, code review and agents that open pull requests, but completion is the feature you meet first and use most.

One wrong answer marks a real boundary worth holding onto: Copilot proposes source code for a human to accept, and does not turn source code into a runnable program. That translation is still your compiler's work, entirely unchanged by Copilot being installed.