Question

what is frictional force.......​

Answer 1

Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact.

Answer 2

Frictional force is a force applied by surface to the opposite side of the motion of body.

Frictional force is also known as Drag

when force is exert by fluid ( air , water).