Assign up to 4 keyboard shortcuts to get straight to the tab(s) with your email, docs or other core content in it.
Assign up to four hot keys (usually CTRL + SHIFT + KEY or ALT + SHIFT + KEY or ALT + Key or CTRL + key) to switch tabs to your favorite websites. If there's more than one tab open with the favorite site, it toggles among them (like hitting Alt + tab). If the site is not open at all, it opens in a new tab.
This is particularly helpful for those of us who have a ton of tabs open and just want to find our most recently-opened Gdoc or Gmail tab with one quick keyboard combo. You can also access the shortcuts by right clicking on the toolbar icon and selecting one of the context menu options there.