MPLS is one of the latest technologies of routing and ip switching
It's very fast because it just tags the packet with a No. then it maps this no. to an ip address so the router dosen't have to inspect the packet it just reads the MPLS tag and forwords it....
Also that's why it's not considered a Layer 3 protocol like tcp/ip nor a Layer 2 protocol like Frame relay or ATM so they decided to put it in an new Layer called Layer 2.5
here is a video training about MPLS