Classic braids are two braids, one down each side of the head. The ends can hang loose, but are often joined together into a single braid or wrapped into a bun and pinned together.
Classic braids work particularly well with shorter hair. Hair that is too short to be pulled back into a basic braid can often be put into classic braids easily, since they do not need to pull the hair as far.
For more pictures of classic braids I've done, see my Flickr set here.