Activate your Cerberus Network card and receive access to exclusive benefits. Revisit the emotionally stirring Normandy SR-1 crash site, recruit the deadly bounty hunter for hire Zaeed Massani, equip the latest gear and firepower with the Cerberus Assault Armor and Eviscerater Shotgun, and pilot the formidable Hammerhead. With more content and updates coming free to Cerberus Network members, make sure you activate your card inside your copy of Mass Effect 2.
Source: Mass Effect 2 Website.
This Downloadable Content is the engine through which Bioware distributes other content for Mass Effect 2, it comes free with new copies of the game or may be purchased if a copy is obtained used.