I have found that John Holts explaination of unschooling is to the point, simple to understand, and sums it up nicely. Below is a passage copied from the website http://www.holtgws.com/index.html
GROUP MEMBERS: Please feel free to answer this question below in the replies, tell us what unschooling is to you and your family....for each of us will vary in our answers, beliefs, and lifestyles.
What Is Unschooling?
This is also known as interest driven, child-led, natural, organic, eclectic, or self-directed learning. Lately, the term "unschooling" has come to be associated with the type of homeschooling that doesn't use a fixed curriculum. When pressed, I define unschooling as allowing children as much freedom to learn in the world, as their parents can comfortably bear. The advantage of this method is that it doesn't require you, the parent, to become someone else, i.e. a professional teacher pouring knowledge into child-vessels on a planned basis. Instead you live and learn together, pursuing questions and interests as they arise and using conventional schooling on an "on demand" basis, if at all. This is the way we learn before going to school and the way we learn when we leave school and enter the world of work. So, for instance, a young child's interest in hot rods can lead him to a study of how the engine works (science), how and when the car was built (history and business), who built and designed the car (biography), etc. Certainly these interests can lead to reading texts, taking courses, or doing projects, but the important difference is that these activities were chosen and engaged in freely by the learner. They were not dictated to the learner through curricular mandate to be done at a specific time and place, though parents with a more hands-on approach to unschooling certainly can influence and guide their children's choices.
Unschooling, for lack of a better term (until people start to accept living as part and parcel of learning), is the natural way to learn. However, this does not mean unschoolers do not take traditional classes or use curricular materials when the student, or parents and children together, decide that this is how they want to do it. Learning to read or do quadratic equations are not "natural" processes, but unschoolers nonetheless learn them when it makes sense to them to do so, not because they have reached a certain age or are compelled to do so by arbitrary authority. Therefore it isn't unusual to find unschoolers who are barely eight-years-old studying astronomy or who are ten-years-old and just learning to read.
Unschooling is not unparenting; freedom to learn is not license to do whatever you want. People find different ways and means to get comfortable with John Holt's ideas about children and learning and no one style of unschooling or parenting defines unschooling,