Plesk is the next generation web hosting control panel system. Plesk is extremely feature rich as well as include an easy to use web based interface (GUI). You create your hosting accounts through your hosting control panel. It's up to you how many email accounts, mysql databases, etc you give your clients and how much you charge them! Make web hosting packages to suit your client's needs and budget. You simply divide up the resources (bandwidth, web space and features) of your server between your accounts. Every account you create also has a Plesk control panel login, which allows your users to manage their own account, without assistance from you.