It’s something you collect and offer to the Statues Of The Seven 😀
Here, you’re talking about Anemoculi, which as you can probably already guess, can be offered to the Statues Of The Seven of the Anemo Archon.
When you offer a certain amount of Anemoculi, the statues level up and you get rewards and increased stamina, which is pretty cool.
They’re a bit hard to get, but not very rare and you need less to level up the Anemo Statues Of The Seven, which can be really useful.
Hope this helped, lol.