The help/hover text says "A list of all 181 Stack Exchange sites", and yes, there are several sites and sets of sites here:
- Current community
- Meta site for the current community
- Top communities in which you participate
- A list of all communities (with a search/filter)
But it also includes several important features for the current site/community:
- Site/community help (also found in the footer at the bottom of the page, but much more conveniently accessed here)
- Site/community chatrooms, which to my knowledge isn't available anywhere else
- Log out, which to my knowledge also isn't available anywhere else
Based on the hover text, it's very difficult to find the the "log out" functionality (as well as chat). I know it's not intentional -- Just an unintended side-effect. I was curious after reading a site-meta "how do I log out" question (without an answer yet, and without a link to the duplicate). I had to look it up myself (since I've never had the need to log out myself).
I hovered over the far-right icon several times while searching for "log out", but never clicked that icon because I never thought "log out" would be under "a list of all ...". I assumed that it would be a hyperlink to stackexchange.com/sites.
Some possible alternative hover texts:
- Site Tools
- Community Tools
Either of these (or potentially something else) would be a very simple change that IMHO would improve discoverability of the features under that icon. I can't be the only one who skipped clicking/expanding that toolbar icon based on the hover/help text, right?