Bards are poet/musicians. In olden days bards were usually employed by the ruling class. Bards told stories, usually of historical events, through their songs and music.
A bard was a lyric poet that was chosen by a higher person like a king or ruler. I found this out by reading 'The Hobbit'. By the way it was the best epic I have ever read!
There are no characters in any of Shakespeare's plays who are called Bard (although there is a Bardolph), but there are one or two references to the word. An example is:"Richmond! When last I was at...