A term originally used to denote storytellers who sang epic poems, nowadays the definition has expanded and is usually used to refer to any poet or musician in a medieval setting. They are often depicted carrying traditional instruments such the lyre or the lute
In many role-playing games and fantasy settings they are usually depicted as a supporting role, being able to use healing magic or enhance their allies with their music.
As with other profession tags tag what you see, just because a character is stated to be a bard don't add the tag unless they are depicted playing or at least carrying their instrument.