ARPU and ARPDAU
Also said as Average revenue per user, Average revenue per daily active user, ARPPU
Total revenue divided by players, over a period. ARPDAU divides one day's revenue by that day's players. ARPPU counts paying players only.
It lets you compare days and test changes, and that is about all. An average of mostly zeros and a few huge numbers describes nobody: if 97 in 100 pay nothing, the "average player" does not exist. Raising it can mean you have found a better offer, or that you have pushed harder on the people least able to stop.
Say it
“ARPDAU went up 12% after the new offer. Split it by spender band before we celebrate: if it's all from the top 1%, I want to look at what that offer does to them.”
Not to be confused with lifetime value
ARPU is a rate for a period. Lifetime value is what a player brings in over their whole time with the game.