Infrastructure-as-a-Service and Platform-as-a-Service offerings can also provide quick, low-cost access to data center resources for software development and prototyping.
They will need cell towers and servers, large data centers, specialized software, legions of trained personnel and reliable supplies of basic resources like electricity and Internet connectivity.
At its basics, cloud computing represents the ability for software developers to cheaply and easily use the resources of masses of servers sitting somewhere in a data center (essentially supercomputers) to do something interesting or useful.