Hello All.
From reading several fourms, there is quite a bit of confusion on the definitions used in the hosting business. I am creating this thread to help explain the terms. This is a working thread so it will be updated as needed.

Root Access
Root Access is the Master Admin User on a Unix system. This is the highest level a user can have.
Overselling
This basically means selling more resources then you actually own. Most hosts practice overselling and if it is done properly, it can help you maximize your potential earnings
Control Panel
In the hosting business, there are several control panels. The most comon is called cPanel, but there are many more. Plesk, Helm, WebMin, ServerCP, etc.
Operating System
Much like home computers, hosting servers also need an operating system. Most hosts will use CentOS (Linux) or RedHat (Linux). Several hosts also choose to use Windows as the server Operating System.

PLEASE NOTE : The System of the server has nothing to do with what you run on your personal computer. If you choose a Linux Host, you do not need a Linux Desktop.
Alpha Master Reseller (Alpha Reseller)
Alpha Resellers can sell Master Reseller, Reseller and Shared Hosting Accounts. This can only currently be done in cPanel, however requires a 3rd party plugin (such as ZamFoo, Deasoft or WHMReseller).
Most Web Hosts who offer Alpha Reseller Accounts often oversell their servers. If you choose to go with an Alpha Reseller Account, please ensure that it is not an "Unlimited" hosting account. These typically dont survive more then a year or two.
Master Reseller
Master Resellers can sell Reseller and Shared Hosting accounts. This can only currently be done in cPanel, however requires a 3rd party plugin (such as ZamFoo, Deasoft or WHMReseller).
Reseller Hosting
Reseller Accounts can sell Shared Hosting to their customers. Most control panels have this ability. Reseller Hosting is typically the starting point or most start-up hosting providers.
Virtual Dedicated Servers (Semi-Dedicated Servers)
These accounts are normally Reseller or Master Reseller Accounts that are placed on a less populated server. Most hosts who provide Semi-Dedicated only place 2-10 customers per server. Because of this, the price is often higher but you will be able to use more resources then a standard account. Think of it as a First Class icket verses one in Coach.