Simple Definition:

Empathy means understanding the feelings and experiences of someone else. It is the ability to put yourself in someone else’s shoes and feel what they are feeling. For example, if your friend is sad because they failed a test, empathy is when you are able to understand how they feel and why they feel that way.

Very Simple Definition:

Empathy is when you understand how someone else feels. For instance, if your friend is sad about failing a test, empathy is when you get why they’re sad.