How does the rotating bolt operation work and what is one firearm that uses this locking system?

In the gas operated system using a rotating bolt it is the back flow of the gasses from the fired round that starts the operation. The AR-15 uses the rotating bolt operation in conjunction with the gas operation. When the gas pushes through the gas tube it reaches the gas port located on the top of the bolt carrier group (BCG) and begins to push it backward. The locking lugs on the bolt face then turn to unlock the bolt from its barrel. The cam pin that sits in a chamber off to the left side of the bolt is sliding out of its channel and into the BCG thus turning the bolt face and unlocking the locking lugs.