Photons or light particles are basically envelopes or packets of energy. Energy from the Sun travels to the Earth as photons. When energy from photons is transferred to other particles different things can happen. For example, if electrons are released we generate electricity, if the energy makes the atoms and molecules in something move faster the object might change shape or feel hot.
Watch the energy videos, and play Photon Invaders to learn more about photons.
Photon