Sowbugs are land-dwelling crustaceans, more similar to lobsters and crabs than bugs. They are very closely related to pillbugs, but differ in the fact that they have two tail-like appendages. They also roll up into a ball when disturbed like pillbugs, but they can only maintain a loose ball, whereas the pillbug can create a tight ball.
Sowbugs lack the capacity to retain moisture, so you are likely to find them in moist habitats during the day, hiding under bark or mulch. At night, they are most active when there is no threat of moisture loss.
Sowbugs feed on decaying material such as mulch and grass clippings. They normally do not present much of a problem indoors. If you find an invasion indoors, there is usually a larger population just outside. Sowbugs usually just last a few days indoors unless there is an adequate food supply and moist conditions.