From Ubuntu11.04's help, it says: What is the meta key? The the meta key is key between the Ctrl and Alt keys on your keyboard. It may sometimes be called the windows key, logo key, system key, or even the Ubuntu key. If you have an Apple keyboard, there will not be a meta key on your keyboard. The Command (Cmd) key can be used instead. The meta key serves a special function in Unity. If you press the meta key, the Dash is displayed.
The main issue with the hoverboard is the battery. According to CNET, most hoverboards use lithium ion batteries, the kind often used in laptops and cell phones. But the liquid inside these batteries is flammable, and hoverboards (which have been produced and marketed out of thousands of essentially nameless factories in China) haven't adhered to a singular set of safety standards, and could very well be dangerous.
Common Battery Types. Lead Acid These are the most common type of batteries used in automobiles and to store solar energy because they can provide high current and their cost is relatively low. They store only about 25 watt-hours per kg. Each cell consists of lead electrodes in a sulfuric acid solution. One lead electrode is coated with lead oxide.