This should clarify the purpose of the update in question:
There is also this LWN article, courtesy of Brian “bex” Exelbierd of Microsoft, for some more background: https://lwn.net/Articles/1079808/
As for the other questions, I think, this thread should have all the answers.
In short, you can just click that notification and the firmware updater will apply the update and ask for a reboot. It’s a pretty standard and safe operation.