The command palette is how you get around and get things done. Open it from anywhere with ⌘K (or Ctrl K on Windows), or by pressing the 3-layer button next to any email.
Then start typing, and the list narrows to the action you're looking for. Use ↑ ↓ to move, Enter to run, and Esc to close.
What it offers depends on where you are. Open it with a conversation selected or open, and you get actions for that conversation. Open it from a list and you get actions for getting around.
Help us decide which version of the command palette we should ship. A menu that is centered on the page, or one which is anchored to the top of the search bar at the top of every page?