Following Monday's Google Play Music launch in Europe, Google's music matching service has been enabled for European users. Similar to iTunes Match, the new service works through the existing Google Music Manager app, crunching your music collection and matching it to stuff already on Google's servers. This bypasses the tedious process of directly uploading music, which until now has been a necessary evil for anyone wanting to move their existing library over to Google's streaming service.
The whole process is designed to be transparent to users, so the only difference you should notice is that the music manager app completes its work significantly more quickly than before. Google Play Music now includes libraries from all the major labels, but if you have any music that's not in Google's collection, you'll still be able to upload that as before.
Right now the scan and match service is only available in Europe, though a U.S. launch is expected soon.