The term web server is used to refer both to the computer on which are hosted the websites and to the software that delivers websites content or performs the required operations to build the dynamic content which is later served to the user.
Let’s see the difference between the two more in depth:
Web Server (Computer)
Every website must be hosted on one or more computers (server, web server): the hardware employed to build this computer can be extremely simple or extremely complicated, groups of multiple servers (clusters) might be used, sharing the load of the requests coming from the web. This particular configuration is required when a website gets massive traffic.
On the other hand a web server can be a computer as simple as your home computer, or a computer with a particular case designed for data center usage. These servers can be mounted inside server racks to optimize space. These servers are usually wide, deep and very thin. The width is 19 inches, it’s standard so that servers can be mounted in any server rack.
Rackable servers can have different heights. The base unit the rack Unit, commonly referred to as U, which is 1.75 inches high. Most common sizes for servers are 1U, 2U and 4U depending on the number of the components (disks, CPUs, ram memory sticks, power supplies etc). As far as it regards their functionality there’s no difference between the two types of servers, the difference is only in terms of space required inside the server farm.
Article Source: http://EzineArticles.com/3883820