Lieutenant Commander Shepard is the human protagonist of Mass Effect, Mass Effect 2, and the upcoming Mass Effect 3, whose gender, appearance, skills and pre-service history are all customizable and have an impact on the story. Shepard's first name is also customizable, but is never stated in-game. The default pre-made Shepard is a male Soldier named John, with the Earthborn/Sole Survivor profile. Female default name is Jane.
Shepard was born on April 11, 2154, is a graduate of the Systems Alliance N7 special forces program (service no. 5923-AC-2826), and is initially assigned to the SSV Normandy as Executive Officer. Shepard later becomes the first human to join the Spectres, an elite special task force for the Citadel Council.
Source: Mass Effect Wikia, "http://masseffect.wikia.com/wiki/Commander_Shepard", available under the CC-BY-SA License.