The oldest form of payment is barter. Barter is a simple form of payment. It is the transfer of one good or service for another.
Today, payment is usually with money, cheque, debit, credit, or bank transfer. There are no limits on what a payment can be. In transfers between businesses, sometimes payments can be complicated, with stock and other things.
In law, the payer is the party that sends the payment and the payee is the party that gets the payment.