A Dedicated server, means that you are dedicating a server only for your purposes. This server is not shared 
with anyone else, and it’s resources are only for your use and purposes. Mostly what you get from a hosting service is servers as part of the same machines (same hardware) where you get a set of resources as you define them, and they might be a part of a stronger machine, where you get only a part of it, and that machine might serve other servers, and other resources.
The Dedicated server means that you get to decide what operating system it will have, which type of hardware etc… which means this is your server, a complete machine only for you, and all of its resources are dedicated to your purpose and the server services you intended for it. That is what a dedicated server is.
Dedicated e-mail server: E-mail servers became very important servers, as e-mails became one of the most important communication technique used by many. Since e-mails are being used bot
h by regular home users, and of course by companies, the resources required from an e-mail server that serves a huge amount of users simultaneously, it require a great deal of resources to be able to cope with such traffic and load. Creating a dedicated e-mail server, serves that purpose, making sure all of the resources of the server are focused to serve the e-mail server requirements. That way the e-mail server is keeping it services at high availability and performance all the time. The control of the whole resources are in your hands.
The dedicated e-mail server can be either a dedicated Exchange server, or a dedicated Zimbra server (based on Linux), as long as the dedicated server is configured completely for those purposes, to keep the dedicated e-mail server at its best performance at all times.
Dedicated game server: Game servers are usually machines that can cope with many requests at the 
same time. When gamers want to play online games, they usually connect to a server hosting those online games, such a server if it will be a dedicated game server, it will be able to cope with all of the enormous amount of traffic, as many online gamers all around the world, get online and use it’s resources to run their game application.
Since a distant gamer connects to the server and gets the game application resources from the server he connects to, that server needs to be able to cope with the processing capabilities of a graphical game requirements, including very fast graphic cards, that can process all those amazing graphics, computer games have today. So a dedicated game server for that purpose is what you will need, that way you will have the full control over what and where to adjust the resources from the game servers to be able to adjust the setting in such way, that your computer online game, will work perfectly for all participants.
Dedicated collocation server: The collocation server is actually a collocation center. This means that this server is a type of a “Data Center” that enables multiple connections, at a cost benefit way. The idea is multiple servers share resources and data center infrastructure using large scaled powerful machines. This powerful machines enable best performance and less latency, that enable businesses to focus on their business instead of the high performance network problems. Making sure this collocation server is a dedicated one, enables the full control I mentioned before and of course the full use of all of the resources.
Collocation Hosting Places:
• http://www.nyi.net/colocation.html
• http://www.ubiquityservers.com/
• http://www.colocationamerica.com/
• http://utropicmedia.net/
Here are some places where you can get a dedicated server hosted:
• Eukhost
• Hivelocity
• Bodhost
The Dedication part means that the server is solely yours, and the definitions you require for it, like bandwidth, security, resources and other configurations that you have requested, will be dedicated to you, so you will always have them available.
You will need to define, the bandwidth you need, the hard-disk capacity allocation requirements, the memory (RAM) you require and CPU needs (2 Processors (Duo) or 4 Processors (Quad)) and the kind of dedication server you require – if it’s a Dell server or HP or whatever the hosting offers and you find suitable.