It is real world test done by the group of user before the final deployment to find as many defects as possible.
The main purpose of pilot testing is to catch potential problems before they become costly mistakes.
It is the testing done by end users before the final release when the development and testing are essentially completed.
The purpose is to find final problems and defects.
is done at the client side and all end users use the system and see whether the system is working as per their given requirements. This is done after pilot testing is successful and the defects found in case of pilot testing are fixed.