A call center is a physical place where customer and other telephone calls are handled by an organization, usually with some amount of computer automation. Typically, a call center has the ability to handle a considerable volume of calls at the same time, to screen calls and forward them to someone qualified to handle them, and to log calls. Call centers are used by mail-order catalog organizations, telemarketing companies, computer product help desks, and any large organization that uses the telephone to sell or service products and services. Two related terms are virtual call center and contact center. Customer service is a cornerstone of most businesses, a large part of what keeps customers loyal or sends them running for the competition. For years, businesses have used metrics to measure their call center operations, such as number of calls answered, length of call and call resolution. Those metrics worked fine -- for a while. This guide also examines the prominent role social media now plays in the call center, and how metrics have been expanded and updated to keep in step with the march of time and technology.