Here's why:

* Like poles repel: Magnets have two poles, a north pole and a south pole. The fundamental rule of magnetism is that like poles repel and opposite poles attract.

* Magnetic fields: Magnets create invisible magnetic fields around them. These fields interact with other magnets.

* Repulsion: When the south poles of two magnets are brought close together, their magnetic fields interact, creating a force that pushes them apart.

Think of it like trying to push two ends of the same magnet together - it's difficult!