Launched in 2011, Origin is EA's digital distribution platform. It's widely considered a rival to Valve's service, which a couple of years ago. Origin initially launched to some mixed reviews, but EA has since revised its privacy agreements and seen adoption of the platform skyrocket due to wisely tethering some of its marquee games to the service. Battlefield 3 and the download version The Old Republic, for example, are Origin exclusives. At its presentation, EA's COO Peter Moore stated that Origin has over 21 million users.
What can you do on Origin? Origin has its, ahem, origins in the EA Store and is primarily used as a way to purchase and download games, including many non-EA titles. It's client software that you install on your computer that self-updates. You can also add games to Origin that you've previously purchased, and see what games your friends are playing, invite them to play, etc.
EA has stated numerous times that they want to launch an Origin mobile app, further knocking down barriers between mobile gamers and conventional desktop games. This is especially critical for the Mac gaming community, as the line between Mac gamer and iOS gamer has largely blurred. Apple's hasn't been a critical success, and if EA can build a better mobile social gaming app that has cross-platform functionality, it's looking at not only dominating the Mac gaming market, but the more lucrative iOS market as well.
Origin will be entering an already crowded field of digital game distribution platforms available for the Mac.