"Addon Domains" within Cpanel allow you to host additional domains from a single hosting account. The drawback to this is that each addon domain shares the main Cpanel account, and as such only one person usually has access to control everything. This is fine if you're a single person hosting multiple personal sites, but what if you're, say, a web designer or developer, and would like to create completely seperate accounts for your clients? This is where reseller accounts come into play.
A reseller account allows you to create individual and new accounts that are completely seperate from your main account, based on your main account package. You are responsible for setting how much diskspace*, bandwidth* and other features they receive during the account creation process. These accounts receive their own Cpanel login details, and appear completely seperate from your main account. They are, of course, however linked internally so that we know who they belong to.
As a reseller, you are responsible for providing hosting support for any clients that you may add hosting for. We will only deal with the reseller directly and cannot support any of their customers or clients.
*The diskspace and bandwidth usage of these client accounts are extracted from your main account package. Whilst there is no limit on the number of accounts a reseller may create, they can never (combined) exceed more than the resellers main account package.