Windows 10 updates - how it works?

[shu-hi]

So, I check for Windows Updates and click the button that says "Check for Updates" and it comes back with "Your computer is up to date".

So I close down my computer and turn it off for the night.

I wake up in the morning and I have a Windows update ready to be downloaded and installed. 

So how does this happen when my computer is shut off?

[GamingOptional]

Either HP Support Assistant or Windows Update got you that Update information as you were signing in or...

your PC was actually in Sleep mode.

In Hibernation mode the PC won't wake for updates but in Sleep mode it will, you'd need to disable the Wake Timers in your Power Plan(both while plugged in and on battery) to stop that from happening.

[shu-hi]

I never use Hibernation mode or sleep mode when I shut down my computer. All the options in the Power settings are set to NEVER so nothing is shut down (monitor, hard drive, battery) unless I completely shut off the computer. 

The updates have always arrived (and will this time as well I assume) but I never see that they are available until I turn on my computer. Just curious.

Thanks for your reply