I always forget them, so I have this bookmarked: https://support.mozilla.org/en-US/kb/awesome-bar-search-fire...

TL;DR:

Add ^ to search for matches in your browsing history.

Add * to search for matches in your bookmarks.

Add + to search for matches in pages you've tagged.

Add % to search for matches in your currently open tabs.

Add # to search for matches in page titles.

Add $ to search for matches in web addresses (URLs).

Add ? to search for matches in suggestions.