MPLS is Multi-Protocol Label Switching.
So, what is Multi-Protocol Label Switching?
I ran across this acronym recently when reading about Miscrosft Azure. MPLS can be used to create a virtual network tunnel between your intranet and the Azure network. The main benefit is that it allows packets to be forawrded at the Layer 2 (or, switching) layer instead of the Layer 3 (or routing) layer, thus is can really speed things up. It can be a big benefit when connecting two private networks together over the internet, as the lower latency and higher speeds can make the two networks perform and function more like a single local network.