Stereoisomers which are non-superimposable mirror images are called:

Enantiomers

Stereoisomers which are non-superimposable mirror images are called Enantiomers. 

The stereoisomers related to each other as non-superimposable mirror images are called enantiomers.

D and E are enantiomers.

Enantiomers possess identical physical properties namely, melting point, boiling point, refractive index, etc. They only differ with respect to the rotation of plane polarised light. If one of the enantiomer is dextro rotatory, the other will be laevo rotatory.