Bandwidth is the amount of data your site uses in a month. It’s usually based on the number of visitors you have. The more visitors, the more bandwidth you need. If your website has large files like video and images, you’ll need to be aware of bandwidth limits as well.
When starting your website it’s easy to overlook the most important factors when looking for a web host since many hosts advertise tons of features which you will probably never use. Many providers offer inexpensive packages by overselling their servers and cutting corners on hardware and service quality. This has a negative impact to the quality of hosting you are receiving from those providers.