Question

why does compass needle get deflected when brought near a bar magnet ?

Answer 1

due to the magnetic field produced by the bar magnet .
the compass is also a type of magnet so the magnetic field when produced by the magnet intersects with that of the compass.
they both act like two bar magnets.

Answer 2

    A compass needle is a small and weak bar magnet. A bar magnet creates a magnetic field around it. When the compass needle is brought near the bar magnetic, the magnetic field exerts force on the compass needle. The compass needle aligns itself along the direction of the magnetic field line at that point.

   The deflection of the compass needle is due to the attractions of opposite poles and repulsion due to like poles.