Voltorb is a spherical Pokémon that resembles a Poké Ball with eyes and minus the button. The top half is red, while the bottom half is white. Because of its resemblance to Poké Balls, it is thought that it was created when one was exposed to an energy pulse.

This is supported by the fact that its components do not occur naturally. Voltorb is generally found in power plants and other areas with electric fields where it feeds. It was first discovered in the plant where modern Poké Balls were invented. It has a volatile temperament and will explode if agitated or bumped by the slightest contact. Due to being constantly mistaken as a Poké Ball, Voltorb has reportedly zapped many humans as a result.

Forms
Voltorb has a regional form: Hisuian Voltorb.

Hisuian Voltorb, like their modern counterparts, resemble the Poké Balls of the time period (made from Apricorns), having the same wood grain pattern and a hole on top, from which it discharges all of its stored electricity while lacking the latch. On the inside, they contain numerous seeds, but it has been impossible to examine their interior due it being pitch-black. Hisuian Voltorb has a distinctive red wooden unibrow.

Unlike Kantonian Voltorb, they have friendly and excitable temperaments, which leads them to cluster around people, causing them to be a nuisance when they discharge. It is known to let out a great, uproarious laugh whenever it discharges. Hisuian Voltorb can store electric currents in its belly. There are stories of people temporarily plugging the holes of Hisuian Voltorb to prevent them from discharging before removing them from their settlements. Despite the resemblance to Poké Balls however they have existed since at least the time of the ancient hero long before Poké Balls were invented.

Evolution
Voltorb evolves into Electrode.
Hisuian Voltorb evolves into Hisuian Electrode.

(Source: Bulbapedia)