what is centrifugal foce?

Centrifugal force is a fake force applied on a body negotiating at circluar motion.

EG;

When u sit on a merry go round.  You experience a mysterious force pulling you away from then center, this is known as centrifugal force. 

its magnitude : (mv²/r) away from the center along the radius

a force equal and opposite to the direction of centripetal force which only comes into play in an accelerating frame (non-inertial).
centripetal and centrifugal forc does not cancel eah other!
centrifugal force is just a pseudo force which is req. in an non inertial frame to make it work intertially,
it shall not be counted if the frame of refrence is inertial.

Centrifugal force is the apparent outward force that draws a rotating body away from the source in a rotating frame..

 it is type of psuedo force which is generally used in circular motion.

Centrifugal force (from Latin centrum, meaning "center", and fugere, meaning "to flee") is the apparent outward force that draws a rotating body away from the center of rotation. It is caused by the inertia. of the body as the body''s path is continually redirected. In Newtonian Mechanics, the term centrifugal force is used to refer to one of two distinct concepts: an inertial forece (also called a "fictitions" force) observed in a non-inertail reference frame, and a reaction force corresponding to a centripital force.

the force that act oppoite to centripetal force

in other words, peudo force in circular motion