How can I use the flight control board?

I am making a quadcopter and I am in some confusion. I am planing to get a KKv3 Flight Control Board from Hobby King. The question is, if I get the board then what is the need of getting a seperate IMU6050 as I have seen in some projects that people have used the 6050 sensor along with the Flight Control Board. Is it necessary to use that? As the flight control already have sensors on them. Also, does the flight control board gets connected to the arduino? and if so then how?