A step down is just like it sounds. Instead of having to travel a great distance the majority of the travel is down a steep slope, with the booter being at the top of the slope. There is very little danger of decking, but you can still hurt yourself. If you are not comfortable with this size of jumps, I would suggest getting cofortable on smaller tables or backcountry booters first.
'Say what you will about the tenets of modern socialism, at least its an ethos' -Walter Sojezch, The Big Lebowski