Business consulting includes the industry and practice of helping organizations improve performance and results through the analysis of existing business problems, development of plans for improvement, and implementation of those plans.  Organizations hire the services of business consultants for a number of reasons, including gaining external advice and access to the consultants' specialized expertise.

Information Technology ("IT") consulting includes the practice of helping organizations improve technology usage through the analysis of information needs and requirements, computer and systems infrastructure, and availability of customized and packaged applications.  Organizations use IT consultants to supplement existing staff, or to perform project-based work

Management consulting is sometimes used as a broader term to be inclusive of both Business consulting and Information technology consulting.  In all instances, this type of "white-collar" or "knowledge worker" consulting - tends to be temporary or project-based work.  Organizations use management consultants for specific skills, to supplement headcount on a temporary basis, or to explore potential ideas and introduce business change.

The "Big Six" consultancies of the 1990's are often associated with large organization's perceptions of what business and IT consulting might include.  Better known consulting organizations of today include Accenture, BearingPoint, IBM Global, Deloitte Consulting, and Capgemini.  These organizations "came from" Andersen Consulting, KPMG, PWC, Deloitte, and E&Y. 

Many professionals (former consultants) have launched careers in these organizations - and are leaders within major organizations, start-ups, or still within the consulting profession.  Some of these consultants have since launched small niche consultancies - sometimes called "singe shingle" shops.

An emerging approach to providing business and IT consulting to organizations is through a network of "single-shingle" organizations - and sometimes through alliances between mid-sized consulting organizations.  One example of this type of network is XBIG6COM, LLC ('xbig6") which derives its name from the "Big Six" described above.