A data center is a computer system's most important and vulnerable component. At its most basic, it is a physical place that houses a computer network's most critical systems, including backup power supplies, air conditioning, and security applications. We're talking a large amount of data here, stored in a large number of computers.
A typical example of a company that almost certainly has a data center is a bank or other kind of financial institution. A bank's data center will have a mainframe or other kind of computer network, on which customers' account information and other data are stored. A university will also have a similar facility, which includes not only personal information about the university's employees and students, but also information on the university's buildings, construction projects, and physical and intellectual history.
These kinds of data centers contain information that is critical to the continued operation of the bank, university, or other business. Therefore, that data cannot be lost. Security measures surrounding such data centers are usually very strong, as are systems of climate control that keep the center's computer systems from malfunctioning. Data centers will also almost certainly contain backup computers or mirror drives that protect against massive data loss. Such backup computers or mirror drives are routinely dependent not only on electronic power but also on battery power, so that they can continue to function in the case of an interruption of electronic power.
Other kinds of data centers can be found in government institutions; companies that have multiple headquarters; and providers of electronic services such as television, mobile phones, and the like. A data center can also be a single computer, storing and accessing one company's or one person's critical data. Smaller centers usually have less complicated forms of data protection.