When you purchase a hosting package, it comes with a certain amount of disk space and monthly bandwidth.
Disk space usage is basically a total of all the files stored in your hosting account. This includes your website code, images, emails, etc. As you store more files, the disk usage goes up.
For example, if you add 10 images of 100 KB each, to your website, the disk usage would go up by:
10 x 100 KB = 1 MB (approx.)
Bandwidth usage is the total data that is transferred between your website and your visitors. Bandwidth usage goes up depending on the number of visitors you get, and the number of pages each visitor opens on your website. Bandwidth usage also goes up when you visit your own website or use your Content Management System to update your website content.
For example, if each page on your website is 500 KB and you get 1,000 visitors, your bandwidth usage would be:
500 KB x 1,000 = 500 MB.
The bandwidth usage counter is reset on the 1st of every month.
If you have almost reached your bandwidth limit for the month, you should consider upgrading your hosting account.