While "other businesses" might seem like the simple answer, Dwyer and Tanner (2006) say business customers fall into four broad categories: companies that consume products or services, government agencies, institutions and resellers. And
The first category includes original equipment manufacturers, such as large auto-makers who buy gauges to put in their cars and also small firms owned by 1-2 individuals who purchase products to run their business. The second category - government agencies, is the biggest. In fact, the U.S. government is the biggest single purchaser of products and services in the country, spending more than $300 billion annually. But this category also includes state and local governments. The third category, institutions, includes schools, hospitals and nursing homes, churches and charities. Finally, resellers consist of wholesalers, brokers and industrial distributors.