You can see the penalty kick as a form of direct free kick which means that a goal may be scored directly from it. If no goal is scored the game continues on as usual.
The penalty kick rules were invented by the association of football (soccer) and is a type of free kick taken from 12 yards (11 meters) out from your opponent's goal with only the goalkeeper and you (the penalty taker).
If your opponent commits a foul punishable with a free kick within their own penalty area (also known as the box or the 18 yard box) or a handball your team will be awarded with a penalty kick.
I remember my first soccer match. My coach told me that I will play left back and said even "Whatever you do, don't commit a foul inside the 18 yard box."