Aleš Lombergar

As the others have so well pointed out, it is method of accurizing your rifle. If the wood touches the barrel, after a few rounds and the barrel heats up, your point of aim gets off, because the barrel bends where it is touching the wood. If the imperfections are eliminated, no more barrel bending. I prefer the remove the wood between the fore end and lug , making an air gap. This can be tested on some designs by inserting a dollar bill between the stock and barrel and drawing it towards the lug. If the bill doesn’t hang, you need to do nothing.
The removal of a small amount of wood is a tedious process, so bedding is the lazy man’s way of achieving the same thing.
I’m using the term lazy loosely there, because it is every man’s preference as which to do to achieve the same effect.

No matter how well it’s done, there’s some imperfection in the fit between the action and the stock. It can shift slightly and thereby affect accuracy. Glass bedding puts an epoxy resin and fiberglass filler in the interface between the action and the stock. The barrel can still be free-floated or left with a contact point at the forend. I’ve had rifles that didn’t need it, rifles that wouldn’t shoot without it, and one stock that I broke when I didn’t use enough releasing agent when I bedded it.