eah so my understanding is that Tor relays your traffic through several computers in the middle, which make it near impossible to determine from the exit node who originated the traffic.
VPN's act as a sort of extended ISP that that can track who made the connection (if logging is enabled) to trace it back to you.
The Tor browser also has built in protections within the browser software to protect you from other scripts and plugins that can give away your true source IP.
That being said, Tor is better for anonymity but if you wanted to you could use both a VPN and Tor, even a proxy chain if you really wanted to go crazy.