ANSWER:

Disk space is the size your web site can be. Every single letter on your web site has to be stored somewhere on a server. Each letter is one byte, and a megabyte is roughly one million bytes. HTML pages are usually very small, but it is the extra images, scripts, and even databases that can take up large amounts of disk space.

Bandwidth/Transfer is the amount of data the server will allow your site to send in a month. Transfer is usually measured in gigabytes - billions of bytes. Integral Hosting, it's only $1.00 per gigabyte!