Solar Panels are made of many solar cells connected in a series.  Silicon solar cells or photovoltaic (PV) cells convert light into electricity.  The cell is created when pure silicon is combined with phosphorus or arsenic to produce a negative charge (N-type silicon) or boron to create a positive charge (P-type silicon), then grown into a large crystal in a furnace.  The crystal is sliced into film thin strips and treated with the opposite element to create a neutral cell, 1 positive side and 1 negative side, producing no electrical charge.

The neutral silicon crystal film is now a Photovoltaic cell.  When exposed to light, electrons flow from the negatively charged layer of the crystal to the positively charged layer.  The flow of electrons creates electricity.  The electricity is channelled in series to a common output, which provides DC (direct current) electricity.

Solar cells can be used for many common applications.  Solar lights are PV cells that charge a small battery which provides the electricity at night to power the light.  Solar water heaters use the converted sunlight to produce electricity for the heating element.  Many solar panels can be used in an array to provide power for a residence or business.

If a solar array  is tied into a battery or off-grid system, it will charge the unit and power can be used without conversion.  Any excess electricity produced will be stored in the batteries.  However, you can not use more electricity than your panels will produce.  The batteries will simply run out of charge.

If the solar array is tied to a power grid, the DC current will need to be converted to AC (alternating current).  Any excess electricity in a grid-tied system will be fed back to the grid as surplus.  Some power companies will compensate surplus at a rate that is different than the cost of consumption.  But even if they do not, if you produce more than you consume, your meter will run backwards and you will receive a credit.