How does the relative wind on a propeller, strike the blade from behind (the non camber side)? This may be a stupid or simple question, although any help is appreciated! :) 

If possible, please answer without mathematical terminology. So I understand the concept of the blade increasing air momentum at the front, thus creating lower pressure, and I also get that the blade acts as an airfoil, lower pressure at the top, and higher at the bottom thus pulling it forward, and producing thrust. 

My main issue is that I can't visualize how the relative wind physically travels behind the camber side, and hit the back side of the airfoil like in the diagram? Wouldn't it hit directly on the camber side if it's moving forward, not travel below, and strike it from the back? If someone can explain, that would be amazing!
Plane moving forward plus blade moving down gives us a combined velocity vector, shown above in red.

Relative air(speed) is still coming from ahead—but this now no longer concerns the propeller as it has its own velocity vector.

Tilt your head (or check right image to avoid neck injury) and you'll see the blade's angle-of-attack. Remember, air (shown above in light blue) comes in from the direction opposite to the velocity vector.



Increase forward speed, velocity vector changes, angle-of-attack is now smaller, but the airfoil is also faster.