The first time I came across this word was from my camera club's email a couple of weeks ago. Honestly, that was the first time I ever heard about hyperfocal distance. It is a big word, no doubt. When I googled it, I saw the scientific explanations for it. It didn't make me any wiser straightaway.
After more research into it, I have made up my own explanation for this concept. Forget about the theory and technical explanations. The chart on this page will explain clearly what is necessary to know, unless you are a theory fanatic.
First, a short explanation about hyperfocal distance. It is the distance where, if you focus on a subject at that point, the focus is at its sharpest from some distance before it, and the infinite distance behind it. This technique is desirable to achieve large depth of field for landscape photography. The chart explains it all. Notice that this chart is for a specific sensor size, and for an 18mm focal length. A different chart can be generated for each sensor size and/or each focal length.
Note that hyperfocal distance and depth of field are closely related. While the hyperfocal distance is a fixed number for a set aperture, the depth of field varies depending on distance to the subject, up to a point, that is. Beyond that, the focus is at infinity. This can be observed by reading down the columns in the chart. (Click on the chart to display the image in full size)