10 GB is a lot of bandwith. Usually you won't get over this amount - except you offer a freebie everyone wants to have ;-). What counts for bandwith: ftp transfer (when you up- or download files to your webspace), the traffic that is generated, when visitors come to your website, emails send from your website using an email form, filedownloads from your website (i.e. when you offer some freebies). Usually there should be a FAQ somewhere on this providers site where all this things are explained in detail.

Every organisation rests upon a mountain of secrets ~ Julian Assange