Stereoisomers are a type of isomers that have the same chemical formula and connectivity of atoms but differ in the spatial arrangement of their atoms. They can be categorized into two main types: enantiomers and diastereomers. Stereoisomers differ in their configuration, which is the three-dimensional arrangement of atoms in space. The correct answer is c) Configuration.

Differences between stereoisomers:

1. Composition:
- Stereoisomers have the same composition as they have the same chemical formula and the same atoms. The number and types of atoms in stereoisomers are identical.

2. Constitution:
- Stereoisomers also have the same constitution, which refers to the connectivity of atoms in the molecule. The bonds between atoms and the overall structure are the same in stereoisomers.

3. Configuration:
- The primary difference between stereoisomers lies in their configuration. Configuration refers to the spatial arrangement of atoms in the molecule. In stereoisomers, the arrangement of atoms in space is different, leading to distinct physical and chemical properties.

4. Steric hindrance:
- Steric hindrance is not a differentiating factor between stereoisomers. Steric hindrance refers to the repulsion between atoms or groups of atoms caused by their close proximity in space. It is related to the bulkiness of substituents around a particular atom or group of atoms.
- While steric hindrance can play a role in the stability and reactivity of stereoisomers, it is not the defining characteristic that distinguishes them from each other.

Conclusion:
In summary, stereoisomers differ from each other in terms of their configuration, which refers to the spatial arrangement of atoms in space. They have the same composition and constitution, but their three-dimensional arrangement sets them apart. Steric hindrance, on the other hand, is not a distinguishing factor between stereoisomers, but it can influence their stability and reactivity.