Amazon selling help? Do i have to pay for shipping to send my item to the buyer or does the buyer pay for it?

someone brought a videogame with a 3.99 shipping fee. Do i have to spend 3.99 for the shipping and ill get the money returned with the shipping every 14 days or does they buyer spend the money? like is the shipping price on the label i print out with their bank account information or something? how does the shipping work when i want to send a item out to the person it was sold to?