Clarify error vs unchecked exception

Author: Bahaaio

concepts/exceptions/introduction.md

@@ -131,7 +131,8 @@ Current balance: 5.0
 Java also has a separate category called _Errors_ which are serious problems that are external to an application.
 An example of an error is the `OutOfMemoryError` which occurs when an application is trying to use more memory than is available on the system.
 
-Like unchecked exceptions, errors are not checked at compile-time and are not usually thrown from application code.
-Unlike exceptions, Errors represent serious system-level problems that applications should generally not attempt to catch or handle.
+Like unchecked exceptions, errors are not checked at compile-time.
+The difference is that they represent system level problems and are generally thrown by the Java Virtual machine or environment instead of the application.
+Applications should generally not attempt to catch or handle them.
 
 All errors in Java inherit from the `Error` class.