The term covers the full spectrum of how travelers plan, book, and purchase travel, whether through travel agencies, online, or directly from travel suppliers. A supplier (such as an airline) employs various ways to put their products to market. Some use 800 phone numbers and Web sites, whereas others use travel agents as their retailing arm, but most use a variety of direct and indirect means to reach leisure or business travelers. There are a series of intermediaries that comprise travel distribution. For instance, these middlemen can be automation-related as is the case of the GDS (Global Distribution Systems), or sales-related as with agents or tour wholesalers. The suppliers decide, based upon yield and revenue management, which intermediaries to use and they evaluate the best automation to get the distribution job done. Travel distribution is a complex series of relationships with the end goal of all involved to make sales to travelers.