First of all, we have to establish one thing here. I'm not necessarily talking about bandwidth in the sense of speed of transmission or data transmission rate (bits/second), which is the correct definition for the term "bandwidth". I'm mainly talking about the so called bandwidth which measures the total amount of transmitted data (bits).

This whole misuse of the term bandwidth probably has its causes in the fact that most packages come with a specified amount of Gigabytes/month. Some might have considered it to be the same thing as bandwidth because the it is measured in bits/second. But who really knows?

Still, in order to be clear and rigorous I must make a clear distinction between terms. Bandwidth means data transfer rate, which is a speed - the speed of transferring data. Hence unlimited bandwidth would mean, in other words, an infinite speed when transferring data. This does not exist. Speeds are limited in our world. For example we (or at least most of us) believe that the speed of light is the ultimate speed of anything in this universe. However, the speed of light is limited, not unlimited.

Back to definitions, when most hosting companies refer to bandwidth in their shared/reseller hosting packages they actually mean "data transfer", not "data transfer rate". They state for example 5GB of bandwidth, meaning that you'll be allowed to transfer 5GB of data, usually within a period of time of one month. This is the data transfer that you are allowed to use (or consume), the amount of data that is transmitted, not the speed at which it is or can be transmitted. The thing that really boggles the mind is perhaps that they offer it at a fixed price. Can you put a fixed price on something unlimited? In fact, the very idea of unlimited in a limited world seems... well... rather impossible.

Your usage of bandwidth should be seen as unrestricted not infinite, because there still are 2 main indirect limits in place. One, that doesn't often get mentioned, is the fact that the network, as good as it might be, and the server's connection, still have limited capacities. The other, and most often to be encountered, has to do with other server resources usage levels such as CPU and memory, but also input/output load (basically the hard drive being able to serve the files as fast as it is requested to).

Really should learn before you offer free hosting