1.Solar Thermal (Hot Water) – Collectors absorb sunlight to heat water. 
Solar water heating typically feeds into your conventional heating system. Cold water from either your well or municipality is heated by the free energy of the sun, and then moves on to your conventional water heater - electric, oil, gas, propane, or wood fired - for any additional heating that may be required.
2.Solar Thermal (Hot Air) - Collectors absorb sunlight to heat air. 
Solar collectors are also constructed that heat air. The hot air developed in such collectors can be used directly in the home during the daytime or stored in massive materials (rock or water).
3.Solar Thermal (Power) - Solar energy can be used for more than just heating, they can be used for power generation with steam or stirling engines.