Dear Aakash
An inertial frame of reference (FOR) is a non-accelerating FOR , for  example if a person is observing a moving car while at rest or while  moving at constant velocity, he is in an inertial FOR. A non-inertial  frame of reference is an accelerating FOR for example a rotating FOR. (  Rotation requires centripetal force and centripetal acceleration so any  rotating object always requires a centripetal acceleration to rotate.) 
For more information follow link
http://www.askiitians.com/iit-jee-physics/mechanics/inertial-and-non-inertial-frame-of-reference.aspx


All the best.                                                           
AKASH GOYAL
AskiitiansExpert-IIT Delhi
 
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                      Dear friend!  Inertial frame of reference is that which does not rotate or accelerate. Non inertial frame of reference is that which rotates or accelerates.
						

							
Inertial frame of reference is unaccelerated frame of reference in which Newton' laws of motion are valid.
Non-inetial frame of reference is accelerated in which Newton's laws of motion are not valid.