Some teams are just buddies banded together. Sometimes a team is created for a match play tournament where your team competes against other teams. Sometimes a Team is created for a particular sponsor (Team Discraft or Team Innova), where each member of the team represents and promotes the sponsoring company.
Some teams are easy to join. Others are not. Say you wanted to be on the US Olympic Marathon Team. How much time, money, sweat and pain would that effort take?