Question

why 2 magnatic poles repel each other

Answer 1

A Magnet attracts or repels other Magnets, depending on their mutual orientation of North and South Poles. When placing like Poles of two Magnets together, the Magnets repel each other, Figure 2. However, if opposite Poles are placed together, they attract each other.

Answer 2

When two magnets are placed with their like poles face each other, the lines of the forces are in opposite directions and hence like poles repel each other. When the unlike poles of a bar magnet face each other the magnetic lines of force are in same direction hence unlike poles attract each other.