A surname is the part of your name that tells people what family you belong to. Like how your first name is what people call you, your last name (another word for surname) tells people which family you come from.
Patil is a surname that many people in India have. It's like a nickname that tells others they are from a certain place or have a certain ancestor. It's like how your friends might call you by your nickname to show they know you well.
Patil is mostly associated with a group of people from the state of Maharashtra in India who were traditionally farmers and soldiers. People who are born into families with this surname carry it as their last name throughout their life.
So, if someone has the last name Patil, it means they are most likely from Maharashtra and come from a family that has a farming or military background.