One of the research tasks that seems to be present on most Pokémon's research task is "Number of different forms you've obtained." My initial assumption is this referred to catching the regional variants of Pokemon, but apparently I've already managed to complete this entry for some Pokemon, despite having only caught a few pokemon in the first area. I've noticed that I have two different genders for these Pokemon, so I'm assuming that a Pokemons gender must qualify as one of its "forms". Although now I'm confused what exactly is considered a form, and so I'm looking for some clarification.
What is considered a "Form" for the "Number of different forms you've obtained" research task?