Remote desktop client update? Whats this?

Remote Desktop Client is part of your macOS system. There is no outward-facing app for the client part of Remote Desktop.
That update was provided today for the system.
Not some kind of scan.

It is the client software that resides on any Mac. You would use that when you want to provide comprehensive support for Macs on a network,using the Apple Remote Desktop software. The software allows you to easily do a lot of things on Macs from a central server, or from a controlling Mac, such as a teacher's computer, with student Macs under the teacher's control - or other network setups that have Macs.

It's a small update, which is safe for you to install (it's from Apple)
Or, you can choose to ignore it, I suppose.

 

--- Post Merged, Feb 23, 2017 ---

Thank you I was a little confused.

 

I just downloaded as well, surprised no one mentioned it until now.