Administration in the SharePoint 2013 Environment
SharePoint is a very complex product. In addition to the users of SharePoint, a complete infrastructure also makes up a SharePoint environment. If you use SharePoint Online, then Microsoft handles most of the infrastructure (your organization is still responsible for its own Internet access). If you use SharePoint on your own premise, then there is a small army of administrator roles that need to be considered.
In addition to site (and site collection) administration, there are also SharePoint farm administrators. A farm administrator takes care of all the settings for the entire SharePoint farm. A farm is made up of multiple web applications that can each contain multiple site collections. Depending on the size of your organization, you may have multiple farm administrators.
SharePoint runs on Windows and uses the Microsoft database product SQL Server. These are complicated products in their own right and often have their own administrators. In particular, a database administrator is a very specialized role, and many companies have more than one of them.
SharePoint environments are often made up of multiple servers. And then you have all the users that each have a device that needs to connect to these servers. To make all the communication happen, you need network administrators. Network administrators live in a completely separate world from the rest of the administrators and focus on the wires (and wireless), switches, hubs, and routers that connect all the devices together.
A lot of administrators make up a SharePoint environment. Organizing them all and making everything work properly is one of the reasons SharePoint is considered enterprise-class software.
Using SharePoint on your premise gives you more control over the environment, but using SharePoint Online offers a cost-effective alternative, and SharePoint Online is often the only real choice for small- to medium-sized organizations.