Question: what type of business is chamber of commerce?
Answer: a form of business network

A chamber of commerce (or board of trade) is a form of business network, for example, a local organization of businesses whose goal is to further the interests of businesses.  Business owners in towns and cities form these local societies to advocate on behalf of the business community. Local businesses are members, and they elect a board of directors or executive council to set policy for the chamber. The board or council then hires a President, CEO or Executive Director, plus staffing appropriate to size, to run the organization.