Teetering Head is right, although one of his terms is not quite correct.
Differential Collective Pitch refers to when you push the cyclic forward, the front rotor blades do not change pitch, but the aft ones do.
Confused? Well, consider this... if you push the cyclic forward in a conventional single rotor helo, the disc tilts, the fuselage moves forward and tilts, the pilot applies collective so the aircraft maintains altitude.
If a chinook did the same, and both rotors tilted forward, then there would be a significant fuselage profile would be presented to the relative airflow. To counter this, by moving the cyclic forward, the aft rotor's blades increase pitch and the whole aircraft pitches forward at which time the pilot applies thrust (our name for the collective) which does the same thing as in a single rotor aircraft. (There's also two nifty little DC powered motors called longtitudinal cyclic trim actuators which will tilt the rotor head forward with increasing airspeed which reduces the profile of the fuselage presented to the relative airflow).
Also, just to elaborate, when the left pedal is pushed in, then the forward rotor tilts left and the aft tilts right... and vice versa.
If the cyclic is pushed left, then both rotors tilt left and vice versa.
Like Teetering head said, it's all done with push rods and bell cranks but the pilot inputs are just the same. I recently did a MD500 endorsement and a Schweizer 300 endorsement... and the control inputs are exactly the same. The little aircraft are more squirrelly and manoueverable... but the chinook has tons of grunt and is very quick (140knots).
Hope this helps.
CB