A runner (which I'm not - but it's a good example) cannot just get off the couch one day and decide to run a marathon. You have to work up to it. I've heard a lot of people talk about Couch to 5k as a good starting point. The idea is that you follow the program and it guides you into getting built up into running.
But yeah - that's just one of many programs to assist in people getting their tooshies moving!
