[AC Question]

I want to know when Google backs up or syncs something like a photo or video on the phone to a google account, what does it use to do that? Does it use my connection, so technically, it is the same as uploading? Or does Google use their own server somehow to back things up so I am not using any data?

[hallux]

It uses whatever network connection you are currently on. The "servers" are the remote computer the backup goes to through your network connection. So I guess the answer to your question technically is "both" except no matter what you're using a data connection that you're paying for (your home WiFi or your cellular data).