In the web hosting world, overselling means advertising attributes that a client will pay for, but cannot really take advantage of. Some of the features of a given web hosting plan can belong to this category - HDD space, traffic, database storage space, and many others. A plan may come with unrestricted disk space, for example, but the vast majority of hosting service providers generate accounts on just a single server that can have a limited number of disk drives and considering the fact that all the customers upload content, there won't be any space left on the server eventually or there will be some secret quotas so as to ensure that each and every customer has their share, though everybody has paid for unlimited space. Since most internet hosting Control Panels are intended to work on a single server, many providers don't have any choice but to oversell, that's nothing else but deceiving their customers.