Basically, the trick involves snapping the tail of the skateboard down while sliding the front foot up along the skateboard and jumping. This trick takes a lot of practice to get the technique, but once learned it opens the door for the bulk of common skateboarding tricks.
Alan "Ollie" Gelfand is credited for inventing the rolling Ollie in 1977 as a trick done in pools, and later Rodney Mullen the flatland Ollie in freestyle skating in 1981. Danny Wainwright from England holds the official record for the highest ollie at 44.5 inches, but video footage of a skateboarder named Jose Marabotto from Peru shows Jose ollying a stack of skateboards. Many think that the stack should be over 50 inches, but as the trick is only in a video, it's hard to tell and unofficial. Like most things in skateboarding!