The acronym “BASE” was coined by filmmaker Carl Boenish, who filmed the first BASE jumps (from El Capitan, in Yosemite National Park) in 1978, and actually died some years later while BASE jumping. They used parachutes.
Now this extreme sport--which may be more correctly coined extreme stunt work--is taken one step further. They still use parachutes, but during the first freefall part of the flight, these Wingsuit Base Jumpers use a wingsuit.
The more experienced they are, the closer to the mountains they stay.
If you look at the photos, it all looks a bit static. But look at the video!