Coinbase is a payment provider similar to PayPal but offering transmission of funds in bitcoins. As a merchant platform, it offers subscriptions, reporting, and daily fund sweeps to your bank. It also offers embeddable payment elements for your website and handles transaction completion through callbacks. Customers can easily make payments by purchasing bitcoins in their own currency; Coinbase then guarantees you will receive the dollar amount you quoted for the goods.
Most retailers who claim to accept bitcoin actually use a payment provider like Coinbase or BitPay and never themselves handle a single bitcoin. Here are working sample hosted payment pages in bitcoin and in dollars.