A self tapping screw which can tap holed by driven into it. The self tapping screw is created by cutting a gap in the continuousness of circular thread on it to generating a groove and cutting edge those are similar on a tap for solid substances such as plastics, metal etc. 
Regular screws won’t be able to use to tap hole in metal substances whereas self tapping are used to hole for hard and depth substances such as metal and plastic. For soft substances like wood etc. the self-tapping can simply tip that tapers into a gimlet point where flute is not needed. 
Some types of self tapping screws are self drilling screws which are used in varieties of different applications such as carpentry, dental surgery implants etc.

A self tapping screw which can tap holed by driven into it. The self tapping screw is created by cutting a gap in the continuousness of circular thread on it to generating a groove and cutting edge those are similar on a tap for solid substances such as plastics, metal etc. 
Regular screws won’t be able to use to tap hole in metal substances whereas self tapping are used to hole for hard and depth substances such as metal and plastic. For soft substances like wood etc. the self-tapping can simply tip that tapers into a gimlet point where flute is not needed. 
Some types of self tapping screws are self drilling screws which are used in varieties of different applications such as carpentry, dental surgery implants etc.