A contact center is a facility used by companies to manage all client contact through a variety of mediums such as telephone, fax, letter, e-mail and increasingly, online live chat.[1]
Distinct from call centers, that purely handle telephone correspondence, contact centers have a variety of roles that combine to provide an all encompassing solution to client, and customer contact. Contact centers, along with call centers and communication centers all fall under a larger umbrella labelled as the contact center management industry. This is becoming a rapidly growing recruitment sector in itself, as the capabilities of contact centers expand and thus require ever more complex systems and highly skilled operational and management staff.[2]
The majority of large companies use contact centers as a means of managing their customer interaction. These centers can be operated in two major ways, the first, by having an in house department responsible for the day to day communications with customers, the second to outsource customer interaction to a third party agency.

Source: http://en.wikipedia.org/wiki/Contact_centre_%28business%29