When I would need to choose one term from all in this FAQ, for which I would like readers to remember, then it would be this one. Back up indicates process of copying and storing important files that are on hard drive to some other medias like CD, DVD, other H.D.D.... Often happens that day after day we take photographs and load our PC with tons of photos not even thinking about action as a back up, because disc error is something that happens to someone else, not you. And all of that works great until one day you can't trun on your PC or even save data from destroyed hard drive. There are two categories of people, those to whom it has happened, and the other to whom wi will happen. Many top photographers have lost to them dear photographs because they didn't do back up on regular basis. So once more for the end, my honest advice. At least once a week do a back up of your new photographs on quality media for storing data.