Word Distinction: Receiving Money

Pay is a general word for the money you receive for work. Income means any money that you receive regularly, whether from work or from rents, etc.
Do you have any income apart from your pay?
A salary is paid monthly into the bank (especially to professional people) and wages are paid weekly in cash (especially to people who work with their hands). Money paid for certain professional service (e.g. to a lawyer) is a fee.
Payola (esp. in American English) is the practice of making a secret or not direct payment in return for a business favour.
That disc jockey expects some payola for agreeing to plug a record on his radio show.