A Survivor is a lone player whose goal is to live until any other faction achieves their Win Condition, be it Town or scum. If the Survivor dies, it loses.
Survivors are not known for getting any kind of compensation to help them achieve their Win Condition.
Sometimes Survivors simply have to live until a certain point in the game (e.g. Day 3) instead of all the way through the game.
Use and Power
Survivor is almost always thrown into games for thematic reasons. Not many people want to play as one. In practice it's worth somewhat less than a Mafia Goon – the existence of the role normally makes the game more favourable to the Mafia (and other anti-town factions) than it would be otherwise.
Whether a Survivor is a burden to the Town is up to the Survivor's mentality. The Survivor can't be too much of a help to the Town or else they will get killed at Night; they can't be too much of a burden to Town or they will get eliminated for sanity's sake. Thus, playing as Survivor requires the player to pace themselves.
One nasty strategy at early ELo as Survivor is to vote a Townie immediately and let the scum perform an extended quickhammer for the win. The existence of this strategy means that the presence of a Survivor means that ELo comes a day early, and thus that killing them is not a miselimination and typically good for the town. As such, Towns typically act as though Survivors were anti-town, and will kill them if their role is discovered. In particular, claiming Survivor before ELo is a bad idea.
Be very wary of Survivor claims at ELo, especially if they're offering to use their Kingmaker position to give town the win. This claim is seen more often from Mafia in a 1:1:1 endgame (fearing that they'll lose due to a Bulletproof Serial Killer also being present) than from actual Survivors. The correct strategy as the Serial Killer in such a situation is to vote for the townie and invite the "Survivor" to hammer for the win (unless you are in fact capable of dying overNight).