Almost synomymous with Ceilidh or Hoe Down, a Barn Dance is usually an informal gathering of people for some event (anniversary, birthday, community event, charity event etc.) where a band and a caller entice people onto the floor to dance circle, square, set or line dances.
The venue should have power and lighting and facilities. Catering is left to the organiser and is often an 'American Supper'. Genuine barns are nice for atmosphere but often lack power and facilities, are cold and quite dirty and also quite dangerous. Check the insurance.
Some barns have been restored as proper venues and these are good options. The most usual venue is the good old village hall. They are cheap to hire, have everything you and the band need and are easy to find!