Sunlight travels to Earth in the form of photons. Photons have an energy that solar panels can convert into electrical energy. This electrical energy can then be used to power your devices or home. A higher level description of this process can be found below.
A solar panel is made of a collection of photovoltaic (PV) cells. PV cells absorb photons from sunlight and convert the photon energy into electrical energy. Most PV cells are made of a semiconductor material called Silicon.  Single junction PV cells are made with two different layer types. On one layer the semiconductor is doped with impurities that allow it to have an excess concentration of electrons (called n-type). The other layer will be doped such that there is an excess concentration of holes (called p-type). Holes are atoms that have a shortage of electrons.  When the layers are placed next to each other an electric field is created. A photon must have enough energy to free an electron for current to flow. That amount of energy is equivalent to the band gap energy of the semiconductor.  The electricity generated takes the form of direct current. An inverter is used to convert the direct current into alternating current. 
As you can see in the figure above Michigan has fewer solar power plants than other states. This is attributed to weather conditions in this area. Areas of the country that have more sunlight have more solar power plants. The graph below shows how solar power generation has changed over the last 40 years. There has been exponential growth nationally over the last fifteen years. 
Table 10.8 below shows how cost of solar cells and modules has steadily decreased in recent years. As a result you will see the number of solar shipments exponentially increase.