hi there,
welcome to netlify! Bandwidth is made up of any content that your site serves.
If each page on your site “weighs” 500kb, and your site has 10 pages, then one first-time visitor will incur 5000kb ( or ~0.5mb) of bandwidth if they view each page, more or less (content that is the same on each page will only be loaded once by your browser). I say “first time visitor” because the first time a requestor loads the site, data is stored in an intermediate storage called a “cache” to speed up repeat visits, so not all content is freshly loaded each time.
More info on how we bill for bandwidth: