A Multiple Listing Service is best defined as an agreement under which a market's competing real estate brokerages cooperate with one another to help people buy and sell property. In most states, participation in the service requires local-board membership in the National Association of Realtors.

The term MLS listings refers to the compilation of all properties that are under contract to be sold by local members. There are likely other homes for sale in the market, but they are being sold by individuals not bound by the ethical codes, brokerage-compensation guidelines and other business practices established by the listing service.

The underpinnings of the MLS listings concept date back more than 100 years to when brokers verbally exchanged information about homes for sale in regularly scheduled meetings. Later, MLS listings were recorded and shared in various printed formats - ultimately evolving into biweekly publication of MLS listings books. These books became a mainstay in the home search process for more than 40 years.

The development of the MLS listings concept significantly advanced the professionalism and efficiency of real estate sales; and the concept continues to serve that purpose today.

As business computer use increased, brokerages were able to provide more timely inventory updates to better assist customers and clients. And in today's Internet era, brokers are able to make non-confidential MLS listings data available almost instantly via Web sites and e-mail.

It's important to understand that the public is not accessing a complete Multiple Listing Service database, which may contain confidential information about properties, such as the owners' schedule, security issues or other showing-related details. MLS listings seen by consumers include only particulars that will help buyers in their home search.