Servers do many important tasks, a high quality server like Microsoft Project Server is capable of handling following tasks:
1. Work Management
2. Demand Management
3. Portfolio Analytics & Selection
4. Resource Management
5. Schedule Management
6. Financial Management
7. Time & Taks Management
8. Collaboration
9. Issues & Risk Management
10. Reporting and Business Intelligence
11. Program Management
Source: epmainc.com/microsoft-project-server.html
There are mail servers, FTP servers, Web servers, DNS servers, DHCP Servers, those are the most common types
Web Servers Mail Servers Application Servers
Most servers have what's called a RAID-5 array. Some examples of servers are network servers which allow many computers to use the same network, game servers which are used by game companies and allow thousands of people to play their game at the same time, and telecom servers which control your phone service and possibly your cable service.
Dedicated servers are more secure than shared servers. On shared servers anyone is able to access the server, whereas with dedicated servers, only those who are authorized can access the server.
E-Mail, FTP, & Web Servers all use DNS Servers to find clients and servers!
4 servers.
Clustered servers are servers that all exist on the same network connection. If a number of servers are contained within the same room and are on the same connection, they would be considered clustered servers.
Private servers are non-official copies of the live servers. They are often buggy and out-dated. Please note that these are NON-BLIZZARD servers, if something happens on them Blizzard entertainment can not do anything about it. These servers are illegal.
nothing
to my knowledge there are 1500 servers
Unfortunately, yes there are people who run private servers for world of warcraft. Keep in mind that these servers could be several patches behind the live official servers, and the Game-Masters of these servers follow no rules unlike the official servers. The economy of the private servers is nearly non-existent because of the amount of people on them compared to the official servers.
No, there is not any good servers for Minecraft 1.6.6. In fact, there are no more 1.6.6 servers at all. There are only updated servers. My recamendation is for you to update minecraft. All of the servers, or the most active, always update.