It's Apple update time (no, put down your wallet) for the iOS as well as Watch OS.
The iOS 11.0.2 update is fairly small but fixes some smallish bugs. If you noticed crackling sounds in the audio on your iPhone 8 and 8 Plus during calls (or any other time), it's not your ears. The update fixes that as well as, according to the documentation, the bug where attachments on S/MIME encrypted emails wouldn't open.
Apparently some users have also seen an issue where some photos were hidden and the new update fixes that as well. Updating is as easy as going to Settings> General> Software Update.
For watch OS 4, the 4.0.1 update is only for Apple Watch Series 3 watches at the moment so don't be worried if you have an older model. This software tweak is to address an issue with the WiFi on the latest watches where the watches would connect to unauthenticated networks that needed logins. As you couldn't login via the Watches themselves, this left the phones stuck in connectivity limbo.
If you do have a new Apple Watch, just open the Watch app and head to General >Software Update.