Due to the nature of the series, Commander Shepard can be either male or female (named by the default settings as either "John" or "Jane"), and can have varying histories such as being Earth-born, a "Spacer" or Colony born. The default Shepard is male, (although this default is only applicable in Mass Effect 1) Earth-born and the sole-survivor of a devastating battle. Despite the customizable options, several facts remain true across all "Shepards"; he/she was born on April 11th 2154 and is a graduate of the N7 System Alliance Special Forces Program. Shepard was assigned to the SSV Normandy as an Executive Officer after graduation. During the events of Mass Effect 1, Shepard became the first human Spectre; an elite force that work on the behalf of the Citadel Council.
As aforementioned, Shepard's pre-service history can alternate greatly. The Spacer background involves the fact that both of Shepard's parents were in the Alliance military, as a result of this, Shepard's early childhood involved traveling from outpost to outpost, cluster to cluster. Never staying in one place for more than a couple of months. Shepard followed in the footsteps of his/her parents and joined the Alliance military at the age of eighteen. The Colonist background involves Shepard being born, and growing up, on the Planet Mindoir, which was a small human colony located in the Attican Traverse (itself located near the Terminus System). The Atticus Traverse was the "frontier" of Citadel-controlled Space, beyond it's borders lay the systems populated by the relatively minor non-citadel species, which are generally regarded as being less-civilized as those species represented by the Council. At the age of sixteen, Batarian slavers raided Mindoir and killed Shepard's closest family and friends. During the massacre, Shepard managed to evade capture until a passing Alliance patrol responded to the rescue plea and rescued Shepard. Two years later, Shepard signed up the Alliance Military. Finally, the Earth-born history dictates that Shepard was raised as an orphan, and drafted into a life of petty crime and underworld dealings. At the age of 18, wanting to escape this life, Shepard enlisted with the Alliance Military.
Following on from the early life history, it is possible that Shepard's psychological profile, as based on key events in his/her service record, can differ between three possible choices of Sole-Survivor, War Hero and Ruthless. The Sole-Survivor profile states that during Shepard's service, a relatively simple mission resulted in the rest of his/her unit being decimated in a Thresher Maw attack on the barren planet Akuze. Forced to survive in this hellish environment for weeks before rescue, Shepard underwent immense physical and psychological stress. The War-Hero history states that early in Shepard's military career he/she repelled a Batarian slavers invasion on the planet Elysium single-handedly. Shepard risked his/her life to save many. As an award for Shepard's bravery, the Alliance awarded numerous decorations upon the would-be Commander, a feat that would be repeated time again over his/her military career. The Ruthless history states that Shepard has always adhered to one rule; get the job done, no matter what it takes. Shepard has gained a ruthless reputation, and a certain wariness regarding his/her soldiers, not least because of the battle which took place on Torfan; in which Shepard sent over three quarters of his/her squad to their deaths as well as brutally murdering the attacking Batarians.
The character of Commander Shepard was created by Game Developers Bioware as the main protagonist (and only playable character) to their game Mass Effect, which was released in 2007. Originally an Xbox 360 exclusive, Mass Effect was later ported onto the PC format (in September of 2008) and the Playstation 3 format (December 4th 2012). Commander Shepard's story is the main focus of the Mass Effect franchise, continuing on in 2010's Mass Effect 2, and concluding in Mass Effect 3 which was released on March 9th 2012.
The first game released in the trilogy introduced the character of Shepard, then a decorated Commander regardless of the choices made by the player in the customization system. The game is set in the year 2183, 35 years after humans discovered abandoned Prothean technology on Mars, and some years after the discovery of the Mass Effect relays which allowed faster-than-light travel to be possible to the human race.The Mass Effect relay which existed in the Sol system (home to Earth) was only a small part of a much greater network which connected numerous systems in the Milky Way Galaxy.
At the beginning of the game, Commander Shepard is on board the SSV Normandy, en route to a relatively simple, supposedly low-risk mission to recover the recently unearthed Prothean beacon on Eden Prime. The mission was initially supposed to test Shepard's candidacy for the Elite Special Forces Program titled Spectre, and was being observed by current Spectre, and member of the Turian race, Nihlus Kryik. However, upon arrival it became evident that an unknown alien force was attacking the colony of Eden Prime, and the routine retrieval mission became one of rescue. Upon searching the immediate area, it is clear that Geth forces are attacking, led by the rogue Spectre Saren Arterius. Nihlus confronts Saren, but is killed brutally. After finding the Prothean Beacon, Shepard approached it, only for the beacon to become active and exposing Shepard to ancient knowledge and visions directly into his/her mind. The beacon then deactivates, seemingly destroyed. After the mission, Shepard and the Normandy arrive at the Citadel, and confront the Council with the knowledge that one of their forces as become a rogue. After the initial dismissal of Shepard's declaration, the Commander goes in search of evidence that would prove that Saren is a rogue operative. Confronted with the evidence, the Council instate Shepard as a Spectre, and give him/her a mission; stop Saren.