It taught me the names of a lot of different kinds of crystals, since all the areas are named after them.
I learned I've been pronouncing amethyst wrong. I always thought it was "a-my-thist".
I learned that Giga Drain isn't a TM anymore. Also, I learned that Quash is a TM.
I learned than an epic raid doesn't necessarily have to conclude with a boss battle against the person in charge (I thought during the orphanage scene I'd have to battle Sigmund when I got to his office, but what actually happened was even better).
I learned to take yes/no choices seriously, and not assume it's a rhetorical question that'll loop until I tell the game what it wants to hear. I should probably just assume that everything that happens later will be a result of something I did or didn't do earlier on.
I learned that fangames can have ideas just as creative as the official games. The field effects are so detailed, and I've never seen any idea close to it.
I learned that even the grunts, who don't even have names in the official games, can have a story to tell about who they are and why they do what they do.
I learned about xe/xyr/xem pronouns. I knew about people that didn't identify as male and female, but most of the ones I know use "they", so I hadn't heard of these before.