In basic terms, Center of Pressure is the point at which your lift is applying its vector (direction with force) to the wing of your aircraft. Shape of the wing and speed effects the center of pressure. Symmetrical wings are a good illustration for center of pressure. The camber, AKA curve of the wing, has the same top and bottom of a wing on a symmetrical airfoil so your center of pressure on a level line would be equal on top and bottom. the wing relies on angle of attack (angle between leading edge of wing and forward movement) for lift and adjustment of that pressure in this example.
Also, with center of pressure, you can assume that it will move back towards the trailing edge of the wing as speed increases, and move forward towards the leading edge as speed decreases. Meanwhile, CG stays the same. They discovered this phenomenon back when they were trying to break the speed of sound and discovered the aircraft would violently pitch towards the earth. Look up mach tuck sometime.
Aerodynamics gets really complex but that's what I like about DIY. If you have a fundamental use of basic aerodynamics you can just slap a wing on, balance it and go fly. If you have ever wondered why FT balances the planes around the 20-30% back from the leading edge, center of pressure is your answer. This is the typical location of the CP on basic airfoils but as models and airfoils change, that point changes as well and you have to R&D where you balance the plane for best results.
Unless you have a wing design for diy that has been run through a wind tunnel with very specific mathematical formulas, there is really no way of actually knowing where that point is on your model or where it will be at different speed envelopes. CG is really the only thing we can count on for aerodynamic stability. Just some food for thought.