Need
describe the motion of a pendulum in terms of kinetic and potential energy. as the pendulum moves from its greatest to lowest height and back up again, how does its energy change? when is each type of energy the greatest and the least? what is true about the total mechanical energy of the pendulum?

When you first pull back on the pendulum, and when you pull it back really high the Potential Energy is high and the Kinetic Energy is low, But when up let go, and it gets right around the middle, that's when the Potential energy transfers to Kinetic, at that point the kinetic Energy is high and the potential Energy is low. But when it comes back up at the end. The same thing will happen, the Potential Energy is high, and the Kinetic Energy is low. Through all of that the Mechanical Energy stays the same. 

I hope this helps. :)