A more thorough explanation:

A retail installment sale is a type of installment sale where a consumer purchases a product or service and agrees to pay for it in installments over time. This is commonly used for big-ticket items like cars, furniture, and appliances.

John wants to buy a new couch for his living room but doesn't have the money to pay for it all at once. He goes to a furniture store and agrees to a retail installment sale, where he will make monthly payments over the next two years until the couch is paid off.

Retainage is a percentage of the payment a landowner makes to a contractor that is withheld until the construction project is completed to satisfaction and all mechanic's liens are released or have expired.

Sarah hires a contractor to build a new addition onto her house. As part of the contract, she agrees to withhold 10% of the payment until the project is completed and all liens are released. This ensures that the contractor completes the project to her satisfaction and pays all subcontractors and suppliers before receiving the full payment.