Bare Bones Ascending is a term for ascending a rope with a minimal amount of gear. If you know you'll have to ascend the rope, you should plan for it and bring adequate gear. This will make ascending safer and faster. However, if you get stuck in a situation where you need to ascend, you probably have enough gear on you to do the job with an acceptable level of safety. The method that you choose will depend on the gear at your disposal. Basically all methods use the same general idea. You will create two points of contact to the rope. These will consist of some form of progress capture device. A progress capture device is something that slides up the rope then grips it. It could be a mechanical ascender, a rappel device, or a friction hitch (aka slide-and-grip knot). You'll put your weight on one progress capture device while you slide the other one up the rope. Then you'll transfer your weight and slide the other progress capture device up the rope. In this way, you can gradually make your way up the rope. If you get tired, you can rest. And if one of the progress capture devices fails (like the knot slipping), you'll still have a backup.
Knowing how to ascend a rope with minimal gear could get you out of some sticky situations.
Bare bones ascending is more physically demanding than traditional ascending.
It's also less safe.