BioWare have said though that other platforms and interfaces will be announced in the coming months and you will still be able to gain success in the single player game without having to engage in the Galaxy at War feature.
The multiplayer mode is part of a new feature called “Galaxy at War” which BioWare has fully yet to explain and reveal its full purpose within the new Mass Effect 3 game. You need to target the reaper and once it starts fireing run too the other side, keep doing that run too the sides start out at 1 side run towards the other side and as soon as you can see the red beam about your head height stop and aim. “Players can choose from a variety of classes and races, form an elite Special Forces squad, and combine their weapons, powers and abilities to devastating effect as they fight together to liberate key territories from enemy control.” Alias117 posted on 3:40:53 PM - Report post. However the new multiplayer gaming mode does tie into your Mass Effect 3 single-player game providing you with an alternative method of achieving success in the games main storyline. The announcement was officially posted on the BioWare forums and has unveiled that the new 4-player co-op missions take place outside of the single-player game, and aren’t affected by your Mass Effect 1 or 2 games saves.