DNS Server
DNS Server was created in a collaboration between Gateway Computers and Post Office. A DNS Server interprets and translates a URL to an IP Address.
Network Server
A Network Server was created as a collaboration between Oracle, Sun Microsystems, Post Office, IBM etc... A Network Server is a Computer that let's i.e. a Workstation to run it's OS from a Network Hard Drive Server or download, retrieve or run programs remotely.
Gateway Server
A Gateway Server was made by Gateway Computers. A Gateway Server, handles connection requests and diversions to connect to another Network Server.
POP Server
An outdated and irrelevant server.
IMAP Server
An outdated and irrelevant server.
STMP Server
An outdated and irrelevant server.
Workstation
A Workstation is a Computer that connects to it's Hard Drive connects and stored in a Network Server.