Tamper protection protects all the sep files, folders, running servcies,running processes and registry entries.
Try to kill and SEP process and you will get a Tamper Protection alert.
Many virus as they come to our system they first try to kill AV services and running processes so almost all top AV's have this feature but with diffrent names.
Since Win 64 bits have a diffrent architecture so this feature is not supported yet on 64 bits like PTP.
Just an Update: There is one big issue with Tamper Protection and all Back up Solutions not just SAv or SEP but be it any other AV.
As the backup tries to backup SAV folders tamper protection tries to kill it mking it unusable so you have to disable Tamper protection in that case.