Meaning of VCC?

VCC always stands for the positive power rails. Often, it is the most important rails. Other voltages are then denoted with their voltage or, in your case, simply with "+".

VEE is the negative power rails, and VDD is the common rails. The latter one is not to be mistaken with the ground (but often is connected to it). Then there also can be signal grounds, and digital grounds. These two are ony connected at one point in the schematic. Often near the Power entry.