Payment

A payment is the transfer of something from one party to another. Giving money to a company is a payment, for example. A payment is usually made for goods or services.
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, bank transfer, or mobile payment. 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.