They differ only in how groups are rotated about single bonds. Because at room temperature there is free rotation about single bonds, the conformation of a given molecule will be changing constantly. There are an infinite number of conformations for a given molecule as a result of an infinite number of posible rotations. Enantiomers are not superimposable on each other. Of course, every molecule has a mirror image, but only chiral molecules will have a nonsuperimposable mirror image.
Enantiomers can exhibit diffrent chemical properties, such as very different rates of reaction.
Enantiomers behave differently in chiral, but not in achiral, environments. A chiral molecule and its reflection are shown. Notice that the two are not superimposable and the two stereocenters have changed configuration. Diastereomers are stereoisomers that are not conformers or enantiomers. These molecules are diastereomers.