a VPN is simply an encrypted connection between 2 parties. the service you pay for will mask your traffic until it gets to their server, is unencrypted and then sent out onto the web like normal. this keeps your ISP and other local tracking from working. it won't however stop cookies and the other ways you are tracked around the web. it is mainly used today as a way to get around GEOblocking since you can connect to a server in another country and it looks like your traffic is coming from there instead of where you really are.
TOR on the other hand is a totally different beast. here is a good primer to read explaining some of what that is all about.
https://en.wikipedia.org/wiki/Tor_(anonymity_network)
a VPN is plenty for the average user but is not meant to be a totally anonymous connection and won't ever be able to do that for you. TOR is also not as anonymous as it was once thought to be either and depends on a site being set-up specifically to take advantage of what TOR offers. not every site will have an onion address nor intends to have one.