✔ 最佳答案
Neither.
Amazon collects the money from you.
Once you have paid, Amazon notifies the seller to ship.
You receive. Amazon pays the seller once a month.
This works for both buyer and seller. Buyer can use whatever payment they have on file with Amazon. Seller does not need the infrastructure/bureauracy of wide range of payment methods. Amazon makes money in the transfer and also sets reasonable shipping cost (unlike eBay where cost could be small but shipping is large).
Since Amazon keeps the money "in escrow", you have the option to dispute if there is a problem.