A server is a computer or system that provides resources, data, services, or programs to other computers, known as clients, over a network. In theory, whenever computers share resources with client machines they are considered servers. There are many types of servers, including web servers, mail servers, and virtual servers. An individual system can provide resources and use them from another system at the same time. This means that a device could be both a server and a client at the same time.
In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. It improves privacy, security, and possibly performance in the process.
A reverse proxy server or surrogate server is a proxy server that appears to any client to be an ordinary web server, but in reality merely acts as an intermediary that forwards the client's requests to one or more ordinary web servers. Common reverse proxy server providers include Cloudflare and Akamai. Reverse proxy servers help increase scalability, performance, resilience, and security, but they also carry a number of risks. For example, attackers can sometimes use tools such as Censys or Shodan to find out the origin IP address and bypass the reverse proxy server.