auth only vs. final sale for PayPal

Hi all,
Im using paypal website payments pro setup with api.

I've been trying to figure out the difference between the two. From what I've read so far, I've pieced together the following:

auth only means that the transaction must be authorized before being transmitted to paypal.
Is this true?
If so, where is the payment authorized from? The admin interface?

final sale means that the payment does not have to be pre-authorized and is sent to paypal as soon as the customer completes the transaction.
Am I correct here or off base?

Assuming the above is true, would there be an disadvantage to using final sale as apposed to auth only since you could still issue a refund if the customer decided to cancel an order.

Thanks!

No no ...

"authorize" and "capture" are terms specific to the credit card processing industry.

To "authorize" a card is to contact the card company, verify the address, verify that the funds are available, and place a hold on those funds. (similar to renting a hotel room or renting a car)
To "capture" a transaction is to take a transaction that has been authorized and actually "charge" the card for the amount specified. In some cases, one charges a slightly different amount after adjusting for shipping cost differences etc. (see FAQ link below).

In the case of the PayPal module, "auth only", means to only "authorize" the transaction, but not charge the card.
And "final sale" means basically to both authorize and capture immediately.

Related FAQ article: https://www.zen-cart.com/tutorials/index.php?article=164

Thank you very much for the clarification.

This basically answers my question as to which one I need to use.

Thanks!