(1) Define magnetic field . (2) What are magnetic field lines ?

Explanation

(1) Magnetic field : The region surroding a magnet in which the force of attraction and repulsion due to that magneti can be deteced ( using magnet or magnetic substance) is called the magnetic field .
[ Each point in this field has a particular strength. The field at each point also has a definite direction ].
(2) Magneitc field lines along which the iron filing aling/ arrage themselves due to force acting on them in the magnetic field of a bar magnet are called magnetic field lines.
Note : The path followed by the north pole of a compass needle field , such as that of a bar magnet , is called a magnetic field line . It shows how , the magnetic force change from point to point.