No, it's not about the history of a Linux distribution called Solus. It is about restoring your system to a particular state and time. It is like the System Restore in Windows, but only touches the operation of install and remove.
Let say if you mess your system up by removing an application, than you find that your desktop run slower than before. What you can do is restoring the system before you did that.
Check the history first. In Terminal, type
$ eopkg history
You will see a list of operations with number, the type of operation (install/remove), date, and time.
For example, if your last working system is yesterday as shown in operation number #35, than type
$ sudo eopkg -t #35
Reboot your computer. If it does not work, you can try another number as shown in the history.
Read more at Solus Help Center.