Long time Xbox games, just got my Ps4 today. Can someone answer a dumb question? What is this "wallet" and what is its function?

When I buy games digitally on Xbox, I'm used to just getting a notification that my credit card has been charged.

Again, I just got my Ps4 today and I bought a few games digitally... I see that it doesn't "just" charge my card. It charges my card, places that money in my "wallet" then Sony draws the money out of the wallet to complete the transaction?

I don't understand what purpose this serves vs just charging my card directly.