Why the Data Center?
An on-premise data center hosts a collection of servers, that you keep on site to serve your data-storage needs. Some people see this as a disadvantage; you have to purchase the server hardware along with networking hardware. Like any technology, it will age and need to be replaced.
Of course, there are a number of advantages to this model as well. First, you have complete control over your data and equipment. No one, other than your people, have access. Since you own the hardware and software, customizations are much easier.
Finally, if you are running any legacy systems, you can set up an environment that caters to these solutions. This gives you flexibility when it comes to migrating to a newer system on your own terms.