The "classic" ballads, of Scotland and England, have a number of characteristics--not all NECESSARILY in one ballad, but typically as follows:

Of course, to be a ballad, it tells a story, and almost always in the third person.

Typically four-line stanzas
Commonly rhymed ABAB
Often with refrain or burden lines in lines 2 and 4, although sometimes with a separate burden stanza of two or even four lines. The burden lines are sometimes in plain English (or Scots), and sometimes in nonsense syllables, or "mouth music". When in plain language, they often seem to have little to do with the story.

These ballads just report the incidents, to tell the external story. That is, they don't say, "Oh, ain't it awful?" or "Oooh, wasn't she mean?" They leave the reaction to the listener. One exception I think of is in Eggs and Marrowbone", where the last line of the next to last stanza is the punch line to the joke: "Wasn't she a blamed old fool, that she didn't grab that pole?" I see that kind of comment, a wry joke, as a sort of standard exception. There's a similar exceptional line in The Molecatcher's Wife.

Similarly, they don't report what's in a character's mind as (s)he does whatever it is. That's for the listener to infer.

As to the origin and status of the classic ballads, we're getting close to the immemorial argument about "what's a folk song?" about which the less said, the better. Personally, and not claiming that I am "RIGHT", I tend to go with the Child, Sharp et al. parameters of what they were studying. They were studying the evidences of a culture, defining "folk song" for their purposes to mean a song found in the mouths of the unspoiled folk, as it were, passed down and modified by oral tradition among the musically and literarily unschooled, in order to divine the cultural traces untainted by learning or training.

The main aspect in which I strongly disagree with Professor Child and his ilk is the claim that a folk song had no individual author--ever.
Not just that the author was unknown, but that there was none. Folk songs, by their lights, as I understand it, sort of spontaneously appeared. That seems like so much bushwah, to me.

I expect others can point out other classic-ballad characteristics that I'm not thinking of right now.

Dave Oesterreich