"There's a good article about it on Wikipedia too (not ArduCopter specific). http://en.wikipedia.org/wiki/PID_controller"

"Thank you Dave."

"http://code.google.com/p/arducopter/wiki/AC2_Tweaks   and   http://www.diydrones.com/forum/topics/arducopter-tuning-guide Here are some of the basics, have a read :)"

"For a good explantion google PID controller. The letters stand for proportional, integral, and derivitive. It's a feeback loop controller that "learns" over time."

"Thank you."

"http://en.wikipedia.org/wiki/PID_controller Read wikipedia to get an overview of what it is. P I D terms are values that define the motor behaviure in relation to the input control signal. P proportional error : The output power is multiplied to…"

"Well done. That encourages me to get involved. Bit more reading first though."