Barn Dance is a very inaccurate name for this popular social event. The problem is that there is no name that really will describe a Barn Dance.
The name is inaccurate because Barn Dances are not usually held in barns. They happen in School Halls and Recreation Centres, not to mention posh hotels. They sometimes happen in the open air. Just occasionally they take place in barns.
Other names for Barn Dances include "Hoe-down" and "Ceilidh". Hoe-down sounds awfully folksey and "country & western" while Ceilidh is a celtic event which includes far more than dancing.
So, what is a Barn Dance? A Barn Dance is a social gathering which brings together elements of English and American folk- or country-dancing. It is a fun event rather than a serious one. The dances nearly always work to a set pattern which is given by the "Caller".
The Caller is a modern import from America. Until the turn of this century people would be expected to know the local repertoire of dances (and this is still true in Scotland). The Caller makes this unnecessary as s/he can run quickly through each dance before the music starts, demonstrating, if necessary, how the moves of the dance go. There is a set of recognised "calls" such as "Right Hand Turn", "Circle Left" and (of course) "Doh-si-Doh" (which is a corrupted form of the French words for "Back to Back").
The great thing about a Barn Dance is that it mixes people of all ages. While discos sometimes offend the ears (and the bright flashing lights can hurt the eyes) of older folk, the formality of Ball Room dancing may not appeal to the young. But the sheer fun of a good Barn Dance can grab people of all ages, children, teenagers and adults alike and, because "no previous experience is necessary", a good time can be had by all - as long as you are game for a laugh.