Why is deferred billing sometimes called the same as cash?

Deferred billing is defined as one of the technique of sales promotion where organization offers a grace period before the time when the actual payment is made, which consists of an interest-free time if particular payment is done at the certain (defined) date. It is mostly used for the auto and furniture purchases. It is sometimes termed as cash because customers are not invoiced only for certain period of time, after that time, payment has to be made by the customers and they are definitely invoiced and the cash is realized by the company.