Okay, let's look at the heli from behind. Picture it as similar to a plane but the rotor is a wing. On the plane, the right aileron will go down to raise that side and the left aileron will go up to lower the other side. The plane will then bank to the left while moving forward.
Now, the rotor blade on the right goes down and the left one goes up to do the same thing if the heli is in forward flight. If the rotors don't change their position as they rotate, you'll just be flopping from side to side in the same place.
Again, the blade collective on the right increases (pitches the blade down) and the blade on the left decreases. If the rotor doesn't rotate it will act as airplane ailerons, but, since it's rotation places the blade in all positions within a 360 degree movement, the collective must CONSTANTLY change with the rotation to keep the ship moving to the left. So, you want to go left and the rotor on your right pitches down. That tips the ship to the left. As the blade moves into the forward position it goes to neutral pitch and then into negative on the left side. Same as a plane. Right down, left up, move left. As it goes to the rear, again negative going to down on the right side.
In forward flight a heli operates with Cyclic pitch. Understand that the heli is moving forward and the rotor is rotating. One blade is going forward and the other blade is going backward. What cyclic pitch means in forward direction is that the forward moving blade (Into the wind) doesn't need to produce as much lift as the rearward moving blade, thus, the blade moving toward the rear uses more collective than the forward moving blade in order to produce the same amount of lift and keep the heli moving in a straight and level flight.
The only time both (or all 4) blades are at the same pitch is when sitting on the ground idling or lifting straight up.
