What happens when you buy a digital game from Nintendo?

So, I'm curious to understand the process behind purchasing a digital game from Nintendo. When you make that transaction, what exactly happens? Does the game get instantly downloaded to your console, or is there some sort of waiting period? Are there any additional steps or requirements that you need to follow in order to complete the purchase? And what about payment options - are there multiple options available, or is it just limited to a few select methods? I'm eager to learn more about the entire process, from start to finish.