Solar panels are devices that convert light into electricity.
Lots of small solar cells spread over a large area can work together to provide enough power to be useful. The more light that hits a cell, the more electricity it produces, so spacecraft are usually designed with solar panels that can always be pointed at the Sun even as the rest of the body of the spacecraft moves around, much as a tank turret can be aimed independently of where the tank is going. DS1's solar cells are even more efficient than regular solar panels made for satellites because they use solar concentrators.