Infrastructure: The Base On Which Services Are Built
Having the right infrastructure locked down is essential before a data center can be used to provide services customers require.
"Infrastructure" in this case is the servers, storage, and networking gear that allow data center operators--and often their customers--a base on which to run their applications. It also includes the hardware that makes a data center run, including the power supplies, cooling devices, backup power, fire suppression, physical security, and other devices.
It doesn't make any difference if the data center is targeted at a single business's operation or at multi-tenant infrastructures. With the data center hardware, efficiency is just as important as performance.