What even is the pokemon manga about?

Which manga are you talking about? There have been a number of them, some dating back to the beginning of the franchise are still running today.

It has been years since I've read any of them, but most people are actually talking about Pokémon Special/Adventures, which closely follows and expands on the game continuity, The Electric Tale of Pikachu, of which pictures of Misty are regularly posted alongside a couple of other infamous images, and the Pocket Monsters manga, which is a gag manga more focused on Clefairy.

If I had to guess, that shot is from the Electric Tale of Pikachu. It has been years, though.