First of all, please read below blog post to understand basics of Exception Handling in java.
To continue from there, Basically Java default API has hierarchy of java classes to support different uses cases of exceptions.
The parent class of all Exceptions and Errors is Throwable. Please check below pictorial representation of API Hierarchy
The class Exception and any subclasses that are also not subclasses of RuntimeException are checked exceptions.
And all subclasses of RuntimeException and RuntimeException class itself are Unchecked exception. Rest all are Checked exceptions
Examples of Unchecked Exceptions: