As the title explains already. If you navigate to UserCP, and go to the bottom, you can see a label stating, 'My Sessions'. I'm not really sure what this one should represent, but when you click on it, you're lead to a blank page.
Also, the 'Refer A Member' lacks an icon, but since a new custom theme is coming, I don't think it's so much of a deal.
The MySessions plugin is for security measures. If someone has more than one session open on a different IP address, you'll be able to view that session and close it.
Thus disconnecting the other connection from someone else's location. It's only for Administrators and Staff at the moment I believe. I may remove it though, it's been quite an annoyance recently (it sometimes shows that I have 1,400+ sessions).