A consulting firm is a business of one or more experts (consultants) that provides professional advice to an individual or an organization for a fee.
The primary purpose of a consulting firm is to provide access to industry-specific specialists/consultants and subject-matter experts.
Types
There are different types of Consulting Firms serving different sectors. They mainly fall under the following fields, Types of Consulting
On top of the above mentioned divisions, there are consulting firms which serve niche sectors like advertising/marketing/public relations consulting, environmental consulting, energy consulting, entertainment/media consulting, consulting in politics and the public sector, real estate consulting etc.
References
Consulting firm Wikipedia(Text) CC BY-SA