error vs exception

Both Error and Exception are derived from Throwable in Java.
Error represents errors which are generally cannot be handled. For examples:
OutOfMemoryError, NoClassDefFoundError
Exception represents errors which can be caught and handled. For examples:
IOException, NullPointerException
Exception is divided in two categories; checked and unchecked Exception. 
Checked Exception require a mandatory try-catch code block to handle it.
Unchecked Exception mostly represent programming errors (NullPointerException 
or RuntimeException)
Errors are unchecked exception and the developer is not required 
to do anything with these.
All the Errors are Exceptions, but the reverse is not true.
In general Errors are which nobody can control or guess when it happened,
on the other hand Exception can be guessed and can be handled.