When you download the DLC for your console the "Lair of the Shadow Broker" you´ll notice some changes from the main story line as you progress. From the original choices in ME1, the new Shadow Broker will remember those actions you took when you complete sides quests.

At the end of the DLC you'll receive new gear and armor including the DLC bonus content. From there you can visit Liara T'Soni who takes on the role of Shadow Broker thus changing the entire gameplay for Mass Effect 3.

Without the DLC, players will leanr about the Shadow Broker's identity and play the mission While the players who have the DLC will experience a different experience as the ME3 story progresses.