Consulting firm

A consulting firm or simply consultancy is a professional service firm that gives expert advice for a fee. Consulting firms may have one employee or thousands; they may consult in different topics, for example, management, engineering, and so on. Management consultants typically work with company executives and give them generalists and industry-specific experts, usually trained in management or in business schools. Management consultant usually give recommendations for achieving the goals of a company or helps to lead a project of a company. Many consulting firms not only give the recommendations, but also help with implementation, either by the consultants or by technicians and other experts. This is called outsourcing.
Types.
There are different types of Consulting Firms serving different sectors. 
These fields are:
In addition to the above-mentioned fields, there are consulting firms that serve niche sectors such as