Photovoltaics is the technology that turns sunlight into electricity. At its heart are solar cells made of semiconductor material (usually silicon), combined into modules and mounted on the roof or facade. When light hits the cell, direct current is produced. This should not be confused with solar thermal systems, which use the sun's heat to warm water.
The direct current generated is converted by an inverter into standard alternating current (230 V) and fed into the home's electrical system. Whatever you don't use immediately flows into the public grid or a battery storage unit. A meter records both consumption and feed-in. During planning, the roof area, orientation, tilt and shading are analysed; permits, installation and connection by a licensed electrician follow.
Photovoltaics makes sense for almost any home with a suitable roof, especially when a lot of power is used during the day (heat pump, electric car, home office). Apartment buildings and businesses benefit too.
Look for a certified specialist (for example a Swissolar member), an honest yield forecast rather than wishful figures, warranties on modules and inverters, and a properly obtained building permit from your municipality. Common mistakes include a system sized too large or too small, ignored shading and a lack of self-consumption planning. Get several quotes and compare output, components and service rather than price alone.