Sealed class is used to define the inheritance level of a class.
The sealed modifier is used to prevent derivation from a class. An error occurs if a sealed class is specified as the base class of another class.
Some points to remember:
1. A class, which restricts inheritance for security reason is declared, sealed class.
2. Sealed class is the last class in the hierarchy.
3. Sealed class can be a derived class but can't be a base class.
4. A sealed class cannot also be an abstract class. Because abstract class has to provide functionality and here we are restricting it to inherit.