Enantiomers

Enantiomers are a class of isomers belonging to the optical isomers, taht means, they are characterized by differencies in regions containing at least one chiral carbon.
The enantiomers are considered as the mirror image of one another, like it happens with our hands. Therefore, they are symmetric, non-superimposable molecules.

However, when trying to compare two potential enantiomers, it is not always easy to imagine the rotation of the molecules in space, in order to check whether one is dealing with mirror images of one another. So, the best thing to do is to use the definition of enantiomer. This definition tells us that the enantiomers are molecules that differ in the configuration of ALL chiral carbons. Thus, what should be done is:
1. Identify all the chiral carbons present in the molecule.
2. Verify if the configuration of each one differs or stands in the possible enantiomer.
When I speak in different configuration, I am referring to the situation where it is impossible to overlap all substituents of a chiral carbon in the two molecules. If the configuration of ALL chiral carbons is different, they are enantiomers. If there is at least one chiral carbon with the same configuration in both molecules, they are no longer enantiomers.
Finally, by definition, when there is only one chiral carbon in a molecule, and the corresponding configuration is different in the two isomers, these are enantiomers.