Yes it is possible for a buyer to send a payment trough PayPal using a credit/debit card by doing a so called guest payment. However the seller/recipient must have an account to receive the money. So if the recipient do not have an account PayPal will send a e-mail notification explaining that he/she must set up a PayPal account to accept the money and start using them.
To send money without a PayPal account just go to PayPal's front page and from there click the link Send Money> Send Money Online. From there it will be possible to send a payment to any email address.