Base Jumping, or B.A.S.E. jumping is a discipline of parachuting. It evolves the jumper to jump of an object with a parachute. BASE stands for those objects namely Buildings, Antennae, Spans (i.e. bridges) or Earth (cliffs, mountains, etc.).
Base jumping grew out of sky diving, you usually jump from a lower altitude if you base jump, while sky dives are made from 4,000 meters height. In sky diving the interesting part is the time you spent in the air, not the actual jumping and landing. But those are the most important parts in Base jumping. you only have seconds to react. With base jumps you will almost never encounter terminal velocity.
In Sky diving, you usually are in terminal velocity and can stabilize your position with the air flow. This will also help the parachute to open up easily and in a clean way. Since Base jumpers fall at much lower speeds (no terminal velocity), they are prone to tumble, or have unbalanced shute openings. For base jumpers, the way you jump of determines the way you fall, so base jumpers have to care a lot more about small things, you wouldn't’t have to care for in sky diving.
Although base jumping started out from sky divers jumping off objects with their gear, today usually special base jumping gear is used. This means a very fast shute deployment, the shute opens very quickly, no reserve parachute (no need for it), and special break lines etc.
The Paralyzed BASE jumpers that are daring enough to participate in this high risk and high adrenalin sport usually get off the BASE they are free falling from by going piggy back on a fellow jumpers back. There are also times where they will just jump or should we say roll off the edge with there wheelchair. Sometimes they are able to sit at the edge of the BASE and then just get a friendly push off of the edge..
Base jumping itself is not illegal, but the problem is, almost no one allows people to jump of their buildings. So the process of getting into the building and jumping is an illegal activity. Interestingly, once a year at “Bridge Day” the New River Gorge Bridge in West Virginia is open for a grand event of base jumping where almost everyone can jump. In addition this is quite an easy base jump, so a lot of new comers jump here on their first times.