A data center is the department in an enterprise that houses and maintains back-end IT systems and data stores — its mainframes, servers and databases. In the days of large, centralized IT operations, this department and all the systems resided in one physical place, hence the name data center.

With today’s more distributed computing methods, single data center sites are still common, but are becoming less so. The term continues to be used to refer to the department that has responsibility for these systems, no matter how dispersed they are.

Source: Gartner