Bandwidth is one of the most important considerations when looking at various web hosting services. Bandwidth pertains to how much traffic your web site can handle. It refers to the amount of interaction that your web site is allowed with regard to the rest of the online world.
What exactly is traffic? While it does not literally mean cars in this context, you might very well use that analogy. A stretch of road can take only so many cars at a single time. The more lanes that a road has, the more cars it can accommodate.

In the same manner, the more bandwidth (lanes) that you have, the more data (cars) that your web site can handle. That translates to more people gaining access to your web site at any given time. You may also think of it this way – any road can handle a certain amount of cars, and the more cars get on the road, the slower the traffic moves. In the same way, with a given bandwidth, the transfer of data will slow down as the amount of data increases.

So how much bandwidth do you need? There is no straight answer, as many factors come into play. In general, however, you may use this formula:

Bandwidth = average daily visitors x average page views x average page size.

Make sure to include an extra amount for other factors.