In object-oriented ABAP, the self-reference variable ME points to the instance in which the method is currently being executed. In other words, within an instance method, self-reference variable ME points to the object itself.
The best way to understand this is with the help of below example:
In the above code, the instance attribute and the local variable of the method have identical name. By using ME, we access the instance attribute. Without ME, the runtime will consider the local variable of the method.