Most of these data centers contain rows of lockers that are filled with constantly running servers. Most data centers include backup power generators, multiple Internet connections, environmental controls (e.g. air conditioning, fire suppression), remote hands support, and various security devices and staff.
Many of these data centers host different networks that make up the Internet. These networks often meet one another in a data center. These meeting points are called Internet Exchange Points and they allow different networks to peer with one another. The Internet is made up of a bunch of smaller networks all connected to one another, similar to a spider web. The data centers on this map make up many of the points where different networks and Internet service providers connect to one another.