I have been through most of what you need to know to understand how you view a page on the internet. You should by now appreciate that a client pc request a page they may want to look at and that a server computer somewhere on the internet sends the file (webpage that is asked for back to the client.
I now want to go into a bit more detail about the processes the webserver goes through to make this happen. And talk about what you would need to set one up yourself.

What they are
A webserver has both hardware and software so its a computer running a piece of software (a web server application) that sits on the internet with a load of webpages on it waiting (listening)for requests from other clients on the internet it then serves up the files that are asked for. Er thats it.

What software applications are available
THe big noise in webservers . is Apache, 70% of webservers use it Apache has some advantages over its competitors.

Predictaly Microsoft have a poduct IIS (Internet Information Services) this is included with windows so again to a lot of people it is "free" IIS is the other major player.