What is the difference between a checked and unchecked exception in Java?

Check exceptions are for those situations that can be 'checked' $($for example, an index beyond the bounds of an array, or trying to open a file that does not exist$)$

The compiler requires that all checked exceptions are in a try block or in a method with the throws keyword $($but not unchecked exceptions$)$

There was a difference before Java version $1\mathrm{.}8,$ but since then, both require either the throw or the throws keyword

Whether Java will perform the check at runtime or the operator will