This page, which describes the move known as a Mambo cha-cha-cha, is part of the Turnstep Dictionary at www.turnstep.com.
A mambo cha-cha-cha is a combination of a mambo and a cha-cha-cha (also known simply as a cha-cha). A mambo is a two count move: step forward on the ball of your lead foot, then shift your weight and hips backwards onto the back foot. It's easy once you've seen it done.
A cha-cha-cha is done with 2 normal beats, then three half beats, to make the rhythm "one two three-and-four". It can be done in place (like in the picture), or you can move forward or backwards while you do it.
This move is done in 4 counts: