Many web hosting companies offer “unlimited” as a plan feature. It is impossible for any provider to actually provide an unlimited amount of bandwidth or disk space.
Web Hosting is a commodity. The main elements of any web hosting plan are disk space and bandwidth. Disk space is the space you have allotted on the web server to store your website. Bandwidth is an amount you have available to transfer web pages from the web server to the browsers of visitors to your site. Web pages and graphics consume bandwidth or capacity on the web. Bandwidth and disk space cost money.
The network lines that carry data around the web (optic fiber, cable, copper wire etc) have a finite capacity. There is a limit to the amount of data that can be transferred at any point in time. Likewise, the hard drive of a web server has a limited amount of space determined by the physical size of the hard drive.
Many hosting companies claim to offer “unlimited” plans (both disk space and bandwidth), but be aware that there are physical limitations to both disk space and bandwidth. Before you buy an “unlimited” plan, know what you’re getting into.