By formal definition, field mice are the same species (Mus musculus) as house mice, but like mice in general, a variety of cousins such as new world mice (Peromyscus), who are distant relatives of mice and rats, are also included. For more information on our tiny furry friends, see the mice entry.
Any time a new development gets built on land that was previously farm land the previous residents will attempt to take up new living space. If you live in a recently built house chances are good that you'll have a higher rate of these visitors for the first few years. As local wildlife they are part of the food chain for snakes and owls among others.
Note: Mice are achingly timid and have a high metabolism. Wild mice can die of terror, suffering cardiac arrest, simply by being cornered and picked up. Please be gentle if you are dealing with a wild mouse and humane if you are dispatching one.