Does iTunes create a brand new backup each backup, or does it add onto the previous?

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When a new backup is created, does iTunes "add on" to the existing backup, or is a completely brand new backup created? If it is the former, does it do the same after you restore your phone?

Thanks for the help!

 

[Block]

Okay so I found out that it mostly just saves settings.

Now, when you continuously back up your phone, does it create a brand new backup each time, or does it "add on" to the previous one? If the latter, does it still do that after a restore?