I have a simple enough question but I cannot find the answer on Google,
hope someone can help:

What is the purpose of a self tapper screw, and when would one use such
a screw? Can they be used in place of wood screws? What about with wall
plugs?

For example, is an A2 stainless steel self tapper suitable for attaching
downpipe clips to an external brick wall? (With suitable wall plug of
course).


Feeling very confused !

Steve