The hyperfocal distance is used to determine where to focus to maximize depth-of-field, it is the focus point where everything from half that distance to infinity is in the depth-of-field zone.
You can determine the hyperfocal distance by using a calculator, such as DOFMaster Online Depth of Field Calculator.
If you focus at the hyperfocal distance, everything will be acceptably sharp from half the hyperfocal distance to infinity.
For example, for a 18mm lens at f/5.6, the hyperfocal distance is 9.45 feet.
If you focus at the above hyperfocal distance, 9.45 feet, everything will be in focus from half the hyperfocal distance, 4.7 feet, to infinity.
From Jim Beecher at www.photokaboom.com