Magnetic polarity.  Two magnets will attract, or repel, each other. If the north poles are placed close to each other the two magnets will repel. The same happens with the south poles. If the north and south poles are brought together, the two magnets will attract each other.

When a magnet is suspended freely, one side points North. This is called the North pole of the magnet. The other side points South, and is called the South pole of the magnet.

A compass is a magnet used for finding bearings from North.

The Earth acts like a giant magnet. The Earth's magnetic poles are close to, but not exactly at, the actual North and South poles of the Earth (the surface points of the Earth's rotation axis).

Like poles repel each other, and unlike poles attract.

Cut one bar magnet into halves, and each half becomes a magnet with two different poles. You can never create one with only one pole (some scientists think there might be a few magnetic monopoles left over from the Big Bang that created our Universe of space and time).