Self-Tapping Screw is a general name rather than a certain type of screw. A common mistake that the general public make is mixing up Self-Tapping Screw with Self-Drilling Screws.
The point of the Self-Tapping Screw is the major difference between self-drilling and self-tapping.
Self-Tapping Screws are mostly sharp pointed, with no drill point.
Self-Tapping Screws mostly need a pilot hole to be fastened into the object; however, they are capable to penetrate through thin metal sheets.
There are two major types of Self-Tapping Screws.
First, there are the common thread cutting types, used mostly on wood and metal.
This type of screw is to cut through the material that it fastens onto, creating space for the screw to pass through. However, when unscrewing a thread cutting screw, one runs the risk of damaging the threaded screw path, making it harder to reassemble the object again.
The second type of Self-Tapping Screw is the thread forming type, mostly used on plastic. This type of screw will do less damage on the material it fastens on. And the thread forming screws will give a better hold to the material overtime. However, over tightening or breaking the object, is one of the major risk that this type of screw possesses.