What is a simulator?
MPLAB X contains a simulator that emulates the operation of the microcontroller that you have written your program for. The simulator allows you to visually see each step of your program's execution and to monitor the state of the microcontroller's internal memory registers as the program is run. As you can imagine, simulation facility is very beneficial when debugging programs and their functions.
MPLAB X - C simulation tutorial
continues will continue the MPLAB X C tutorial, and demonstrates how to simulate the operation of a project within MPLAB X. When I get the time...