This is an article from WiseGeek which I found to be quite intresting..
A Point of Sale (POS) system is a system for managing the sales of retail goods. The term is used to refer to the software and hardware associated with check out stands, and all of the bundled features which are included. Most retailers use a POS system at their checkstands or counters, and several major manufacturers offer POS systems designed for various types of businesses, ranging from grocery stores to clothing boutiques. Using a POS system makes a business much more efficient, lowering the costs of running the business while improving customer service and making the business more pleasant to work in.
In the retail trade, the point of sale is the moment when a customer walks up to a counter with goods and prepares to purchase them. A POS system handles the transaction, whether it takes the form of an adding machine and a hand written receipt pad, or a complex computer system. Except in the case of very small businesses, a current POS system usually takes the form of a computer system.
The most basic POS computer system is an electronic cash register. The clerk can ring up goods in the cash register and produce a receipt for the customer. At the end of the day, various cash register functions can be used to print out daily reports which are used to reconcile the cash register and to prepare a deposit. More complex cash registers are capable of extremely detailed reports, and they have memory functions which allow users to look up reports from the past, or generate monthly and yearly reports.
A more complex POS system, however, includes numerous bundled features. Many POS systems have inventory management capabilities, where each piece of merchandise is entered into the system so that it can be tracked. Some systems also allow store buyers to generate purchase orders from within the system, using data about sales and product popularity. Time clocks and other accounting features such as credit card verification may be integrated into a POS system as well. Human resources may keep personnel records within the system, in a separate password protected area.
The hardware of a POS system is also distinctive and important. A typical system includes a display screen for the clerk, a customer display, a cash drawer, a credit card swiping system, a printer, and a bar code scanner, along with the computer loaded with the POS software. Custom features may be added or removed, depending on the industry. A restaurant POS system, for example, may have a feature which prints order tickets directly in the kitchen, or a grocery store may have an integrated scale for weighing goods.