Different types of batteries
In most of the electric skateboards on the market, the battery used is lithium-ion, coupled with some electronics so you don't have to pay attention to what you're doing. Plug it, charge it, use it, charge it again. But if you dig a bit more, you'll understand why it's not that easy, especially when building your own esk8.
So let's dig a bit deeper and see how we choose a battery.
First, the idea is to get the nicest power output (watts or W) possible (not too low, but no need to go crazy, we're not building a race car). 1W = 1V x 1A. To get more watts, we have to increase the voltage, the current or both. Increasing the current will generate higher temperatures, which is not the best (especially in electronics as they are really sensible to that). So increasing the voltage is better. But we can't go to super high either, electric motors and electronic speed controllers (ESC) also have limits. The goal is to find a nice balance between all the components.
The usual esk8 don’t go over 12S batteries (~50V) because either the ESC or motor can’t handle more than that. But there are exceptions.