In Master Builder, the players are builders in a small town (represented by 3D cardboard buildings). They try to acquire building contracts, which they then attempt to complete.
The contracts are gained by bidding on them. After that, the buildings must be constructed using workers. Each worker has his own specialty, and you'll need several different workers to complete a building.
Initially, players hire these workers to complete the buildings. Later, these workers can leave them, sometimes because they have been lured away by other players.