What are magnetic field lines? How is the direction of magnetic field at a point determined? Mention two important properties of magnetic field lines.

(N/A) magnetic field line is:
$1.$ $A$ pictorial representation of the magnetic field around a magnet.
$2.$ $A$ path,straight or curved,the tangent to which at any point gives the direction of the magnetic field at that point.
$3.$ $A$ path that would be followed by a hypothetical north pole in the magnetic field of another magnet if it were allowed to move freely.
The direction of the magnetic field at a point is determined by drawing a tangent to the magnetic field line at that point.
Two important properties of magnetic field lines are:
$1.$ They emerge from the North Pole and merge at the South Pole outside the magnet,and travel from South to North inside the magnet.
$2.$ They are continuous closed curves and never intersect each other.