Different between system.ApplicationException class and system.systemE

https://www.c-sharpcorner.com/interview-question/whats-difference-between-system-exceptions-and-application-exceptions

System Exception     
1. CLR throws system exception
2. System exceptions are generic in nature
3. Each system exception has a meaning. You can directly use them or you can derive new ones by inheriting System.Exception
4. Example for system exceptions include SqlException, StackOverflowException

Application Exception    
1. Application throws application exception
2. Application exceptions are not generic. Each application exception has its own customized meaning
3. Application exceptions do not have a meaning for themselves. You have to explicitly derive from them and create your own custom exceptions specific to your application
4. Example for application exceptions include SharePointException, CmsException

For more details check the below links
https://www.geeksforgeeks.org/difference-between-system-level-exception-and-application-level-exception-in-c-sharp/
http://net-informations.com/faq/general/exceptions.htm

Hi Naresh,
Application exceptions are user-defined exceptions. Maybe if the application crashes, we show "System error: Please contact Admin ".

While system exceptions are. NET-defined items, eg., object reference errors.