The hoverboard is a futuristic skateboard. Unlike today's boards, the hoverboard does not need wheels !
The hoverboard we're talking about is the one Marty borrowed from a little girl, at the Courthouse square. It's produced by Mattel. There's a hole in its front part so as to drive the handlebars in. It's also furnished with a loop strap for one foot.
It seems to be the basic Hoverboard, ridden by children when they go for a run. The handlebars sold with it make the hoverboard look more like a child's scooter than a skateboard. It even appears that it's more for the girls because of its pink color and its brand name (Mattel), which makes you think of the Barbie doll.
In the movie, two little girls own such a hoverboard. One owns a yellow board of which we can only see the handlebars, the other has got a pink hoverboard that Marty will borrow.
Eventually, this little girl will give him the pink hoverboard because she's got a Pit Bull. The Pit Bull is fit out with two little reactors which make the foot propulsion useless.
As indicated in its name, the hoverboard moves suspended in the air.
It seems that an unknown force maintains it at about 4 inches (10 centimeters) above the ground. A little impulse with your feet on the ground is enough to make it slide like a skateboard, but in the air !
On its back, you can see 2 cylindrical flat shapes firmly maintained on the board. They look like magnets. It makes no doubt that those 2 cylinders actually allows the hoverboard to stay suspended in the air.
The hoverboard's principle is not really to escape the Earth attraction. Actually, it never lets a solid or liquid surface approach its back closer than a few inches. It's a repulsion system, like 2 magnets do when you confront the two same poles (++ or --). The difference here is that the surface in opposition can be made of various matters (concrete, earth, water, roc, wood, vegetation, metal, plastic...). However, the hoverboard doesn't work as well on the water. It seems to be slowed by liquid surfaces. Moreover, the foot impulse that is needed to move it cannot be done on water.
A most surprising thing is
that the board never turns over !
It is extremely stable. whatever the weight the board supports, it stays always at the same distance from the ground. May it has to support Marty's weight or a little girl's, the board seems to always float at the same height. When Marty jumps on the hoverboard, we can only see a slight movement of the board.
The incredible steadiness of the hoverboard is showed on several occasions :