Commander Shepard is the fictional hero(ine) in the Mass Effect series of video games created by BioWare. Shepard's gender, physical characteristics, and first name are determined by the player, and in effect becomes the player's "alter ego". [1] Bioware also provides a default character model that the player is free to use instead of creating their own.
Background
According to BioWare, Commander Shepard is a veteran human soldier and an Alliance Marine Commander stationed on the SS Normandy, who has seen action in multiple engagements across the galaxy. As a newly recruited Spectre agent, Shepard is assigned the most important missions in the galaxy and authorized to do whatever it takes to get those missions done. Something must be sacrificed in furtherence of the mission, and as all of Shepard's decisions are important ones, people's lives, and the fate of the galaxy, hang on the details of each choice. It is up to the game player to make those choices, and to live with the sacrifices that result.