The Seven are the top super team in both prestige and income. Their existence is the result of Vought-American injecting fetuses with Compound V, a chemical that gives people super powers. The first members of the program were the team leader Homelander, Queen Maeve, Black Noir, Jack from Jupiter, Mister Marathon, the Deep and Lamplighter.
Like any good super heroes they fight the good fight, battling super villains and saving people. Unlike other heroes, however, who do these things because they are simply good, the Seven do them for glory, fame and power. Despite their public image, in reality the Seven are a bunch of jerks who think they own the world and when not performing in front of the cameras they use their powers however they see fit. Homelander himself is believed to have raped Butcher's wife.
During 9/11, The Seven tried to save one of the planes but fumbled the whole mission, killing passengers, crashing the plane and destroying the Brooklyn Bridge. This also resulted in the death of Marathon. However his death allowed a new speedster, A-Train to join.
Later, due to causing the deaths of the granddaughter of Greg D. Mallory, Lamplighter was sacrificed to appease the Boys so that the Seven and the Boys would not go to war. This created an uneasy truce between the two teams, where each group agreed not to directly target the other. However this does not mean that the teams do not indirectly harass each other. In fact, when the Boys were blackmailing the team Teenage Kix, it was Homelander who tipped them off, causing a fight to break out between the Boys and Teenage Kix. This fight did not end well for Teenage Kix.
After Lamplighter's death, they replaced him with the Conservative Christian hero Starlight who was told her price of admission was to orally please Homelander, Black Noir, and A-Train.
Later it is revealed that Lamplighter, although killed, was brought back to life by the Compound V in his body, however he is now a brain dead zombie like creature. However many of his bodily functions still work and he often defecates with no control and plays with himself like a crazed child. He is kept in the lower levels of the Seven's base and they take turns cleaning up his messes.
By the end of the series, the only living members of the Seven were The Deep and Starlight.
In Other Media
The Seven appears in the series. One major difference is that Jack from Jupiter is not a member. Instead the character Translucent takes his place. By the end of the first season, two members are no longer with the team; Translucent(deceased) and The Deep(resigned).