Abstract

Abstract keyord id used with formally unfinished class and methods.

Abstract Class

Provides a base class to some one to extend an actual class.
an abstract class is missing some or all of the method bodies.
an abstract class can have abstract methods that are not implemented in the abstract class, but in subclass you can't use new on abstract class but you can use abstract reference which always point to some extention of the abstract class unlike interfaces abstract classes may implement some of the methods.
through you can't istantiate an abstract class.
you can invokes its static methods.
you can not declare abstract constructors or abstract static methods.

Any subclass of an abstract class must either implement all of the methods in the superclass of beitself declared abstract.

Abstract Methods:
An abstract method is a method which has no implementation,means an abstract method is deliberately missing it's method body.