The Townie is the most basic role in Mafia. Simply put, you are a pro-Town character, who only wins when the town wins. You have no night actions, and can only lynch during the day. Essentially cannon fodder.

The Mafia Goon is the evil hitman for the Mafia. They are anti-town characters who get a night kill and the ability to talk amongst themselves. In order to perform the night kill, all (living) Mafia Goons must be targeting the same character. Mafia Goon kills come after Serial Killer kills.

The Cop is a pro-town character who has the ability to investigate one player every night and learn their faction (pro-town, or anti-town). Note: Serial Killers, and any other Psychopaths, show upas simply 'anti-town'.

The doctor is another pro-town role who has a special night action. Once per night the doctor can choose a character to save, and if that character was supposed to die, they won't. They can also choose to save no one, but may never choose to save themselves.

Unassigned is the role that all players are assigned before the game begins. This role goes away as soon as the game begins, so pay no heed to it.

The Mason is a pro-town character who belongs to a secret brother(or sister)hood. All Masons can talk to each other during the night phase, but get no special action other than chatting.

The Serial Killer is a pure psychopath. He wins if and only if all other players are dead. He gets one kill per night, and his kills happen first, so if the Mafia target the Serial Killer, and the Serial Killer targets one of the Mafia, the Mafia would die, then the Serial Killer. This order is purely to prevent ties.

The Vigilante is a pro-town role who has taken it upon them self to rid the world of evil. They get one kill per night, a kill that happens after all evil role kills, and the Vigilante wins if the town wins.