In Newtonian Mechanics , force is defined as the rate of change of linear momentum . F=dP/dt.Torque is rotational analog of Force,it explains rotational motion of objects and is denoted by tau.
When a net force is applied on an object it starts accelerating in the direction of force ,On the other hand Torque, when applied to an object ,tries to rotate that object about an axis either clockwise or counterclockwise.
for example: When a person operates a hand pump , he applies torque on the axis. the longer the distance(length of the rod ) from the axis ,the easier it is to rotate the object.
Torque is defined as the cross product of the Distance from the axis and the applied force