Why do like poles of a magnet attract each other?

Like (identical) poles of a magnet do NOT attract each other.  Identical poles of a magnet repel each other.  

Not all materials are magnetic.  Iron containing compounds are the most common magnets and materials that are subject to magnetism.  In order to magnetize an object, the atomic domains inside of the object must be lined up.  Simply put, an object is magnetized when the electrons inside of the object become similarly arranged across the entire object.  I've attached a diagram of ordered and disordered domains.  Once the domains become ordered, a magnetic field is produced.  That field has a north pole and a south pole, and it exerts a magnetic force.  When a south pole is brought near another south pole, the forces repel (push) each other.  The same thing occurs when a north pole is brought near another north pole.  The two magnetic poles will only attract (pull) each other if they are opposite -- north to south.