If there was an easy answer, this website would be very small.
Unschooling is creating and maintaining an atmosphere in which natural learning can flourish.Joyce Fetteroll doesn't like "natural learning," so I don't think it will be her favorite. Other people have favorite aspects. It's worth reading a dozen or thirty of them, and trying them out yourself. The beginning of the one above came when I was speaking in Arizona, and it wasn't being recorded, but Roxana Sorooshian was taking notes. She came up later and showed me something I had said, unscripted, that turned out to be the clearest, simplest definition up to that time. I put it in The Big Book of Unschooling. It was:
Unschooling is arranging for natural learning to take place.But in the next few years, it was carried around, turned over, examined, tried out, and polished. I think "creating and maintaining an atmosphere in which natural learning can flourish" is good.
"School is to unschooling as foreign language class is to learning to talk. The first is orderly, thorough, hard and hardly works. The second is chaotic, random, effortless and works like a charm."
When a newcomer was very confused, Meredith Novak wrote:
The basis of unschooling comes from seeing learning as a substantial human drive and seeing that learning depends absolutely on the perceptions of the learner. The second part is what makes everything tricky - you can't control what someone else learns. At best you can work on seeing the world from another person's perspective and try to create an environment which helps that person learn.
You can read lots more at any of these pages: