Passive solar construction involves siting and construction to maximize the energy efficiency of a building. Generally, this involves glazing the equator-facing side of the building (south in the United States) and utilizing interior materials that act as a heat sink. During winter, sun shines into the home, heating the interior mass. During summer, overhangs, awnings, and/or blinds are used to minimize heating of the interior.
Passive solar design can also include hot water systems, solar cookers, solar chimineys, or any design that collects and redistributes solar energy as heat, without the use of mechanical or electrical systems to aid in the conversion.
By way of contrast, photovoltaic panels, which are often placed on the roof of the building and generically referrred to as "solar panels" convert light energy into electricity; these photovoltaics (often abbreviated "PV") would be an 'active solar' system.