What is sprunki?

Hi yall sorry if this post is maybe redundant but I wanted to learn more about sprunki. My girlfriend’s younger brother really loves it and calls me (my name) sprunki. I really want to understand what he likes so if someone could explain to me what’s up with sprunki like the lore and stuff I would very much appreciate some help or some videos maybe that could explain it well! I’m familiar with other stuff like fnaf and bendy and poppy playtime but I can’t keep up anymore😅 help would be greatly appreciated thank you so much!