On this page
Command palette
Press F2 and start typing to run almost anything without hunting through menus.
Using it
F2 opens the palette. Type and it filters as you go; Enter runs the highlighted entry, Escape closes it. Typing something that looks like an address offers to navigate there.
Entries are grouped by what they act on: navigation, tabs, open tabs, zoom, bookmarks, history, downloads, search, scrolling, sidebar, window, workspaces, media and tools, with the things you have used recently floating to the top.
Why it is here
derp hides a lot of chrome by default. The palette is the fallback for anything whose button is not on screen, which makes running with the address bar and toolbars hidden practical rather than awkward.