Why is an object called an instance of a class?

Answer 1

Instance means that an area of memory is reserved for a value and the address is referenced to some name.
So when you instantiate a class, you create an area of memory (instance) and addresses this area with a name, who will be the object

Answer 2

from Google:

instance
noun
1.
an example or single occurrence of something.

An object is a single occurrence of some class

Answer 3

object is like an exact copy of the class.

object has all the function and variables of the class it represents