Your Terms and Conditions section is like a contract between you and your customers. You make information and services available to your customers, and your customers must follow your rules.
Common items in a terms and conditions agreement allow you to:
Spend $500 and get 5% off - Code "500"
Spend $1000 and get 10% off - Code "1000"
Spend $1500 and get 15% off - Code "1500"
Spend $2000 and get 20% off Code "2000"