Imagine you have two toys - one is a red car and the other is a blue car. Even though they look different, they are both still cars. In the same way, molecules can also have two different forms, which look similar but are not exactly the same. These different forms are called epimers.
For example, let's say you have two different sugars – glucose and galactose. They have the same molecular formula, but their shapes are slightly different. This slight difference in shape leads to them having different properties, like taste and how they affect the body.
So just like how you can have different toys that are still the same type of thing, you can have different molecules that are still the same type of molecule, but with slight differences in their structure. These differences, called epimers, can have big impacts on how the molecule functions in the body.