Why do we have to use Catch and Try and in which cases

Answer 1

For handling checked exceptions.

Answer 2

For error checking. See here:https://msdn.microsoft.com/en-us/library/hh279678.aspx

There is also throw. Which will generate an error that is passed to catch.

Answer 3

as Jay said, to catch errors. Say you want to try something, like open a file, but the file doesn't exist.. instead of crashing the program, put it in a try{} and if it doesn't exist catch{} it and maybe tell the user the file doesn't exist.