How a Content Caching Server can be used to supply an update. Preflight checks are extensive, and lead on to other preparation. Finally the boot chime is muted, and the Mac rebooted to allow installation.
mobileassetd
How Software Update settings obtains a list of available updates, and the variants that should contain. How mobile asset catalogues are checked, and preparations made to download the update.
I’m browsing images in the Finder, when my software firewall tells me macOS is trying to phone home to one of Apple’s servers. We all know what that means, don’t we?
The Eclectic Light Company 