When using a Layaway program, the purchased item is not given to the customer until they have completely paid for the item. A credit check is not necessary and there are generally no finance charges, because money is not being borrowed.
Buying something using credit means you are borrowing the money. The most common example is a credit card. When using a credit card, money is borrowed from the credit card company (lender) and the seller gets paid the full amount immediately. Expect a credit check as a requirement before establishing a new line of credit – credit cards establish a maximum borrowed amount for your line of credit.