Remember when people bought newspapers off street-side stands? The newspaper publishers used a technique called “the fold” to encourage buying. The basic idea is this: the most important and interesting news story of the day was plastered across the top of the section. So, if the paper was folded in half and placed so that only this big news story was above this fold, facing upwards, then the papers would be able to draw attention to the most important story. The story would intrigue readers enough that it would call them to the action of picking up the newspaper and hopefully coaxing them into buying it.
How many clicks it takes a visitor to get to the information they seek is an essential number to be paying attention to when you're planning your website. Why? People are lazy. They don't want to scroll. They don't want to plow through disorganized navigation. They don't want to have to read five paragraphs to figure out what your company does. They need to be able to accomplish all those things before they ever click their mouse.