A foster is a temporary placement for our dogs. The foster family is responsible for basic housetraining, socialization, transportation, and temperament assessment of a placed pet. The foster family is the "advocate" for the dog to potential adopters.
We rely on our foster homes to assess the personality of the dog, identify any behavioral issues that need to be worked on, and so forth. The foster family will walk the dog (How is s/he on a leash?), socialize with other pets and people (How is s/he with children? Other dogs? Cats?), and so on.
Some dogs may need to be housebroken or crate trained. This makes the dog more easily adopted. The more information a foster home can provide to us, the more likely the dog will have a successful placement with a family.