A system used to control the sale system. The app will allow the owner to make more flexible dealing with customer and allows your business to accept payments from customers and keep track of sales. A point-of-sale system used to refer to the cash register at a store. Today, modern POS systems are entirely digital, which means you can check out a customer wherever you are. All you need is a POS app and an internet-enabled device, such as a tablet or phone.