To knead or not to knead, that is the question
In order for dough to bake into nice bread, you must develop a gluten structure that can trap the gas the yeast release as they feed on the flour. You can do this in several ways:


Mechanical action (kneading)
Natural fermentation through yeast


There risks to overdoing it in both cases. If you overknead, see   Are there any negative effects to kneading bread dough longer?

If you overferment (overproof) the dough, the yeast will break down the gluten structure completely and you will have a saggy/gloopy mess that can't contain the escaping gas. See this post.

Many doughs can't develop a good gluten structure without at least some mechanical action, so we typically use a combination. Allowing a natural fermentation (particularly with wild yeast or starter) allows for a more flavorful, easier to digest bread as well.