The original Steadicam, the type that uses that copyrighted name, is actually quite simple in concept. The operator wears a special vest, designed to distribute the immense weight of the unit. Connected to this vest, on the right side, if the operator is right-handed, is a spring-loaded arm which, in general operation, crosses over the body to the left. Attached to the end of this arm by an almost frictionless gimbal, is the camera "sled." This sled is designed to counter-weight the camera (to keep it upright) as well as to simply add weight. There is also a small TV monitor attached to the sled so the operator doesn't need to look in the view-finder.
Since the combination of camera and sled is so heavy, the arm is pressed down and absorbs all the jostling associated with hand-held camera-work. If the operator is right-handed, the right hand is placed on the end of the arm to move the camera around and up & down, and the left hand is very lightly placed on the sled, around the pole connecting the camera mount and counter-weight. The left hand is used for panning and tilting.
Watching an experienced Steadicam operator gives one the impression that this is an easy piece of equipment to use, what with how the camera appears to just float along effortlessly. In reality, the profession requires a great deal of skill... A mixture of agility (in getting the camera to do what you want it to) and endurance (in not passing out in the process).