Question

What is pseudo force?

Answer 1

also known as fictitious force whose motion is described using a non-inertial frame 
for eg rotating reference frame

Answer 2

first of all pseudo means false.
pseudo force is a imaginary force acting in a frame which is accelerated.
if you want an example then :
the centrifugal force is one such force which acts away to the center and here the frame of action is accelerated.
this force is opposite to the real force which is on the body.
pseudo force is used to solve problems in an accelerated frame.
and also this force does not cancel out the real force.