I made the switch from PayPal IPN to PayPal Express Check out on Zen Car 1.3.8a , but am not sure which "Payment Action" to choose or what they mean.

Can someone help explain what Auth Only or Final Sale means and how they work?

I noticed during purchase testing with Final Sale selected if I paid via a credit card through my PayPal account the sales is recorded right away in my PayPal transactions for both my payee account and the receiving accout, but if I pay via a credit card and not through PayPal it's still not showing up even after 4 hours. Does it take a while for the credit card company to process the transaction?

And with Auth Only selected no matter which way I pay there is still a wait for the sales to show up in PayPal transactions and I haven't seen them show up yet.

Any help explaining this to me would be most appreciated. Thank you.