1. The problem involves understanding the terms related to payment when a person buys something and pays part of the price upfront. 2. **Down Payment** is the initial amount paid at the time of purchase. It reduces the total amount owed. 3. **Cash Payment** refers to the total price paid in cash, which may include the down payment plus any additional payments. 4. **Period Payment** is the amount paid periodically (e.g., monthly) after the down payment until the full price is paid. 5. These terms are used in installment purchases where the buyer pays part upfront and the rest over time.