Abstraction

Data abstraction is a technique which provides only the required data to be visible or accessible to outside world. For example, making a call on a mobile. the logic behind making the call is not visible to others but it provides an abstract details of just call button to outside world.

abstract keyword is used for classes and methods.

An abstract class cant be used for creating instances. In order to access, it must be inherited from other class. It can have both normal and abstract methods.

An abstract method doesn't have body and it must be used inside an abstract class.

https://www.programiz.com/java-programming/class-objects