He means dev agencies that contract for projects. Agencies act as general contractors, augment your staffing, or provide consulting services. Agencies build who

He means dev agencies that contract for projects. Agencies act as general contractors, augment your staffing, or provide consulting services. Agencies build whole or partial products, often times for stuff that you use on a daily basis. For example, there's an agency with relationships with many YCombinator companies and builds most of their mobile app or web apps.