What does the idiom pull his own weight mean?

Any sort of team or group is better off with a member who can pull his own weight than they are without him/her. A team member who does not pull his own weight slows down or in another way hinders the progress of the team. It's like if you had a sled and you were considering adding another animal to the pulling team, the animal would need to be strong enough to pull considerably more than its own weight to be worth adding. The phrase is most often used figuratively in regard to people in an assessment of whether a team member's contributions to the team outweigh the costs of having him on the team.