Posted 20 May 2011 - 04:06 PM
First things first is to answer what is a server. The definition of a server is any computer that has a server OS installed on it. So the only real thing seperating a desktop from a server is the OS itself. Hardware means nothing as long as it can support the needs of the OS. Servers can provide many services that desktops cannot. Domain creation is a large one since it can then apply multitudes of settings, security, and tracking to the networked computers that are part of the domain. Of course they can supply other services like, dhcp, dns, file hosting, proxy server, email hosting, and a multitude of other services. While desktops can supply some of these services servers are better able to host larger numbers of clients by design and their ability to address more resourses. Keep in mind when looking at a server they mostly just shuffle data so their need for graphics, sound, and other multi media type equipment is almost non-existant. They only need a decent processor, lots of system memory, and a large fast storage sub system. Required system specs are determined by the needs of the OS plus the number of clients that will be accessing the system.
Blades are a way to consolidate large numbers of servers into a smaller space. They are smaller usually 1 to 4 processor based servers that are diskless. The large rack you see is the blade "center" that houses the blade interface, power supplies, IO blades, and possibly the disk sub system. The OS and other data are stored on SAN type storage which can be on the blade center or anywhere else since they are network based.
Get your facts first, then you can distort them as you please.