Final answer:
Vaporeon, Jolteon, and Flareon evolve from Eevee, which can evolve into different forms known as 'Eeveelutions.' Each evolution is triggered by using a specific type of evolutionary stone: Water Stone for Vaporeon, Thunder Stone for Jolteon, and Fire Stone for Flareon.
Step-by-step explanation:
Vaporeon, Jolteon, and Flareon all evolve from the same basic Pokémon, Eevee. Eevee has the unique ability to evolve into multiple different forms, also known as 'Eeveelutions,' based on different conditions. By exposing Eevee to different types of evolutionary stones, it can evolve into these three distinct forms: Vaporeon evolves using a Water Stone, Jolteon with a Thunder Stone, and Flareon with a Fire Stone.