Hello Student ,

A Chiral Carbon is a carbon  which is able to r otate a plane polarized light either is a clockwise or anti-clockwise direction .

A Chiral carbon can be identified if

1. Four Different atoms or groups are attached to the single carbon atom.
2. Three Different atoms or groups and One Lone Pair is attached to the single carbon atom.

hello rajesh 

a carbon atom attached to 4 diferent groups is called chiral carbon. it's an opticallty active state, for clear understanding you could study more about stereoisomers which are isomers produced by optical activity of c-atoms.

hope it helps