Your bandwidth in hosting refers to how many pages and information your visitors can view on your site each month or the amount of data that can be downloaded.
If the average amount of page views per visitor is assumed constant, the allowable bandwidth defines the number of visitors you can support each month before your website begins to slow down.
Disk space refers to the amount of space your site requires on the server. HTML pages are quite small, images and videos take up larger amounts of space.