Husks are human victims that were abducted by the reapers to use against organics.
The Geth are artificial intelligent robots who turned against their creators, the Quarians. They worship these Reapers as gods, and are found often where the Reapers attack.
The Collectors are another victim that is seen in league with the reapers. They are indoctrinated Prothians, the prominent race of beings in the previous purge.
The First Contact War was the violent first meeting of Turians and Humans. There is still animosity amongst both species.
At the center of the galaxy lies a space station, The Citadel, which houses the galactic council of government composed of an Asari, Turian and Salarian leader. Their Citadel Security (C-sec) is in charge of policing the station and its diverse inhabitants.
The Asari, feminine in appearance, are often considered the most influential and respected sentient species in the galaxy, and are known for their elegance, diplomacy, and biotic (telekinetic/telepathic) aptitude. They were instrumental in proposing and founding the Citadel Council.
Salarians, the second species to join the Citadel, are warm-blooded amphibians that possess a hyperactive metabolism; they think fast, talk fast, and move fast.
Known for their militaristic and disciplined culture, the Turians were the third race to join the Citadel Council. They were nominated due to their rol in creating the Krogan genophage. Turian features are avian, making them resemble humanoid birds or raptors. Palavan is their home planet.
The Quarians are a nomadic species of humanoid aliens known for their skills with technology and synthetic intelligence. Since their homeworld Rannoch was conquered, the quarians live aboard the Migrant Fleet, a huge collection of starships that travel as a single fleet.
The krogan are a species of large reptilian bipeds native to the planet Tuchanka, a harsh and unforgiving planet. Due to their rapidly growing numbers, which caused an uprising rebellion again the rest of the galaxy, the turians unleashed a genetic virus, called the genophage, that severely hindered the fertility rate of female krogan and raised the rate of prenatal and postnatal infant death.
The Systems Alliance, Alliance for short, is the representative body of Earth and all human colonies in Citadel space.
Spectres are agents appointed by the citadel to handle more difficult cases that are threatening galactic peace. They are able to complete their assignments by any mean necessary which puts them above ‘C-Sec’ law.
Jane Shepard is a human female who is nominated to be the first human Spectre. Coming from a military background, she was a prime candidate to take up the role. In game, Shepard is the main character and can be male or female with many different background choices. These choices affect your dialogue and relationship with your companions. During the beginning of the second installment of Mass effect, the Normandy is shot down by Collectors, killing Shepard in the process. She is resurrected by Cerberus to lead the fight against them.
Cerberus is a human-survivalist paramilitary group led by the enigmatic Illusive Man. Cerberus' core belief is that humans deserve a greater role in the galactic community, and that the Systems Alliance is too hamstrung by law and public opinion to stand up effectively to the other Citadel races.
Garrus Vakarian, Jane’s turian love interest, had his military training at fifteen, but later followed in his father's footsteps to become a C-Sec officer. He was responsible for the investigation of Saren Arterius, the Council's top Spectre, after the Alliance claimed Saren had gone rogue. He is an expert mechanic.
Mordin Solus is a salarian geneticist, professor, and a former operative of the Special Tasks Group, where he performed reconnaissance and participated in the modification of the genophage. He joined Shepard, and her crew, on the reconstructed Normandy during the second game.
A long-lived krogan mercenary who has had many adventures, Wrex has heard of Commander Shepard on his travels, and respects the Commander as a fellow warrior.
Flight Lieutenant Jeff "Joker" Moreau is the pilot of the SSV Normandy.
While serving aboard the SSV Normandy, Kaidan Alenko was a Staff Lieutenant and head of the ship's Marine detail. He was also an initial member of Commander Shepard's squad.
The SSV Normandy SR-1 (Systems Alliance Space Vehicle Normandy Stealth Reconnaissance-1) was a Systems Alliance starship. She is a prototype "deep scout" frigate, first of the eponymous Normandy class, co-developed by the Alliance and the Turian Hierarchy with the sponsorship of the Citadel Council. It was later reconstructed by Cerberus after it was shot down by the Collectors.
The Enhanced Defense Intelligence, or EDI (pronounced 'Eee-Dee), is an AI created by Cerberus and installed aboard the Normandy SR-2.
The Mako is the ground vehicle aboard the Normandy.
Extranet is the galactic equivalent of the internet.