Two isomers which are mirror image of each other are known as enantiomers.
Two isomers which has different configurations around a single asymmetric carbon atoms are known as epimers. Examples are D-ribose and L-ribose.
The formation of hemiacetal in a sugar generates a asymmetrical carbon with the generation of two epimers in which group is above or below the plane of the ring. These two epimers are frequently called anomers. The anomer with the group above the plane of Ring is called anomer and the other as anomer.