A server is the cornerstone of your technological installation. This is a Computer or device that “serves” applications and data to the rest of your network. Individual machines connect to a server over a LAN (in the case of an on-site server) or a WAN when connecting across the internet. Servers are the norm is Datacenters. A Datacenter allows you to have a redundant off-site server running your services. Usually backed up by multiple power feeds, diesel generators, and multiple paths of connectivity to the outside world. This is important in ensuring the uptime of your service.
Merriam-Webster Online Dictionary
server (noun)1.
one that food or drink - serves
2.
the player who serves (as in tennis)
3.
something used in food or drink - serving
4.
one that serves legal processes upon another
5.
the celebrant's assistant at mass
6.
a computer in a network that is used to provide (as access to files or shared peripherals or the routing of e-mail) to other computers in the network - services