A barn is usually an agricultural building used for storage and/or as a covered workplace. It can also be used to shelter livestock or to store farming vehicles and equipment. Most commonly barns are found on a farm or former farms. Common barn types: stable, bank barn, carriage house, dutch barn, granary, linhay, round barn, shippon, tithe barn, threshing barn. You can read more about barns on Wikipedia.
The barns I’ll be writing about can also be used for other purposes, for example as garages or storage sheds.