It refers to the evaporative emission control system having a small leak. The multiple codes are for small and large leaks, indicating that at some point it was leaking more than others.
Try cleaning and tightening or replacing your gas cap first. Clean all dirt and rust from the tank nozzle lip so it can get a good seal. The check engine/code may not go away immediately, the vehicle may have to run a few predetermined number of "cycles" before the OBD-II system will erase the code. The best thing to do to find out if you fixed the problem is to use the scanner again and clear the code, drive normally and see if it comes back.

They mean you have an Emission Control leak. it could be something as simple as a missing gas cap or a leak at the muffler, Catalytic Converter or pipes.

Google Emissions Control System for your vehichle to get more or less an idea where to look at a diagram of the Emissions Control System. All the codes mean the Computer has detected a leak.