Solar panels are panels capable of collecting energy from sunlight. They are usually made of silicon based semiconductor devices that are based on Albert Einstein's Nobel award winning photovoltaic effect. (Basically, light is made up of particles called 'photons'- when they strike the semiconductor they knock an electron out of the matrix, and this is collected- the flow of electrons forms an electrical current which can be used to power things.)

Solar panels are one way to generate Solar Power, and are used extensively in Space applications.