Magnetism
The poles of two magnets repel or attract each other. Different poles attract each other. For example, if the south pole of one magnet is put near the south pole of another magnet, the magnets will repel each other. This will also happen with two north poles that are put near each other. If a north pole is put near a south pole, the magnets will attract each other until they stick to each other and can be hard to pull apart.