Jolteon evolves from Eevee when it is exposed to a Thunderstone. It can only be obtained by evolving its Basic Pokémon form. It learns mainly Electric type attacks, like Thunder and Thundershock, but also a lot of Normal type attacks, like Quick attack and Tackle.
Because this Pokémon mainly relies on its Speed, it is a quick One-Hit-KO-attacker, although its Thunder attack is not very accurate. Because it gets Double Kick, it has an advantage over ground types that are also part rock, which is nice to have in an Electric type.
In Japan, Jolteon is called サンダース(Sandaasu/Thunders). In France it is called Voltali. In Germany it is called Blitza. In many other countries it is known by its english name: Jolteon.