this section is talking about how a web application runs
A web server is an application which processes requests via HTTP. There are varieties of web server in this world but all of them are designed to solve different problems. The following are examples of web server.
Tomcat implements Java EE specifications and provides a pure Java environment for Java code to run in
Apache is a very old and famous web server in the world.
Its language interfaces support Perl, Python and PHP.
Apache has dynamic modules to extend the core functionality.
Nginx focus on high concurrency, performance and low memory usage.
It can also act as a reverse proxy server for HTTP, HTTPS, SMTP, POP3 and IMAP,
as well as a load balancer and HTTP cache.
Nginx has statistic modules to extend the core functionality.