This is Pokétools.
Accurate tools and data tailored to each version.
This is a site dedicated to sharing information about various Pokémon games.
There are certainly many sites around dedicated to this purpose. However many of them are only accurate to the latest version, or aren't organized in a clear manner. This site's goal is to present each game's data as a "snapshot" - guaranteed to be accurate to that game when it was released.
Navigate the site using the navigation menu, or try searching!