An exception is an event, which occurs during the execution of a program that disrupts the normal flow of the program's instructions.
The class Exception and its subclasses are a form of Throwable.
All the subclass of Exception class (except Sub class of RuntimeException) are called checked exceptions.
Checked exceptions need to be declared in a method or constructor's throws clause if they can be thrown by the execution of the method or constructor and propagate outside the method or constructor boundary.
Exception extends Throwable
Unchecked Exception extends RuntimeException
Checked Exception extends Exception