There is so much to this extension but the most basic feature is visualizing code authorship. It shows you who made the last change to your current line, the commit message, and when the change was made. Other features include visualizing file history, navigating through git history, rebase editor etc.

AI-generated code autocompletions. Start typing and Copilot will generate code suggestions based on your input. Very often when you start typing the name of your function, it just autocompletes the entire function for you. It's hard to overstate how great this extension is. Does anyone even code without Copilot anymore?