I saw it the second I joined and I'm confused as to what it is? Can someone please explain what exactly that is?

Spirit is a sort of grading system for how active in the game you are. Those who do their daily challenges, beat hard speedrun challenge levels, and even those who just wander about in free roam levels all achieve EXP. When your EXP reaches a threshold, you'll level up your spirit. Leveling up your spirit gives you Bopimo Tokens, as well as spirit exclusive clothes! The maximum spirit you can have is 15, but that might change depending if the game devs think 15 is too low. Hope this helps!