Time Machine: What gets backed up?

Time machine saves MacOS and added Applications and every Users's files on every attached drive (but you should check that this is set correctly) that is MacOS formatted.

Time machine does NOT back up Windows drives, or drives in Windows formats such as ExFAT.

Saving MacOS itself is an option. In my opinion, re-Installing macOS is a frequent debugging tool, and MacOS can be replicated, fresh, in around an hour from fundamental sources, so I do not choose to dedicate the 30GB or so the MacOS saving.

EDIT: I see Limnos is of a similar mind regarding saving MacOS itself.

Time Machine Volumes are NOT bootable, except that they should contain a Recovery partition on the Volume, that can boot to Utilities/Installer/Restore.

Macs after about 2011 have Internet recovery in their ROM, except the 2010-2012 silver tower Mac Pro models.

Restore your Mac from a backuphttps://support.apple.com/en-us/HT203981

Typically everything except system files. You install the system separately, then restore other files from the backup.

None of the mentioned methods generally requires you to re-download your added Applications, unless you choose to do so. If you use Time machine, you can either restore everything (which can include MacOS itself or not, your choice).

Or you can selectively restore just certain categories of stuff, using Migration Assistant or Setup Assistant.

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Leroy Douglas Prefers making Bootable Clones, as he explains in the User Tip:

How to create a boot clone - Apple Community

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