In Java, an exception is an event that occurs during the execution of a program that disrupts the normal flow of the program's instructions. When an exception occurs, it typically causes the program to terminate abnormally, unless the exception is caught and handled by the program.

Java provides a mechanism for handling exceptions through its built-in exception handling framework. The framework involves the use of try-catch-finally blocks that allow you to catch and handle exceptions that occur during the execution of a program.

In Java, exceptions are represented by objects that belong to classes derived from the Throwable class. There are two main types of exceptions in Java: checked exceptions and unchecked exceptions.

1. Checked exceptions: These are exceptions that must be caught or declared in a method's signature. Examples of checked exceptions include IOException and ClassNotFoundException.

2. Unchecked exceptions: These are exceptions that do not need to be caught or declared in a method's signature. They are usually caused by errors in the program's logic or environment. Examples of unchecked exceptions include NullPointerException and ArrayIndexOutOfBoundsException.

Some other important concepts related to Java exceptions are:

1. The try block: This is the block of code where an exception might occur.

2. The catch block: This is the block of code that handles the exception. It is executed when an exception is thrown within the try block.

3. The finally block: This block of code is always executed, whether or not an exception occurs.

4. The throw statement: This statement is used to manually throw an exception. It is used when you want to signal that something has gone wrong in your program.

By using these mechanisms, you can handle exceptions and provide meaningful feedback to the user in the event of an error.