. The use of virtual keyword is to enable or to allow a class to be overridden in the derived class.
. The use of sealed keyword is to prevent the class from overridden i.e. you can't inherit sealed classes.
. The use of override keyword is to override the virtual method in the derived class.
. The use of abstract keyword is to modify the class, method, and property declaration. You cannot directly make calls to an abstract method and you cannot instantiate an abstract class