The server is a computer wich serves information to other computers. These computers, called clients, can connect to a server through either a local area network (LAN) or a wide area network (WAN), such as the Internet.
There a lot of different types of servers, database servers, web servers , mail servers, virtual private network servers. And they all using for different kinds of operation performance. I would to describe shortly the servers wich I mentioned before and write what they are doing. So the first one is Web server .
A database server is a computer program that provides database services to other computer programs or computers. Basically database server is analyzing, storing, archiving and manipulitang the data. A mail server is an application that receives incoming e-mail from local and remote e-mail users and forwards to another server which delivers the massage to another user.
The e-mail server uses SMTP protocol for e-mail receiving.
And the last one I will describe is VPN server (Virtual private network server). A VPN is a secure, private communication tunnel between two or more devices across a public network . There are two common types of virtual private network, which are remote access VPN and site-to-site VPN. Remote access VPN is very common VPN service that you can set up in your office or home network. It can be implemented by setting up a VPN gateway or server and you can connect to it by using VPN client from other locations. Site-to-site VPN is the VPN connection established between 2 VPN gateways that reside in 2 different networks over the Internet, so that both networks’ computers can exchange data securely. There is no VPN client needed on user computers. The VPN connection will be established between both VPN gateways. Both VPN gateways will encrypt and decrypt the communication data to ensure the security and integrity of data. It aims to avoid an expensive system of owned or leased lines that can be used by only one organization.