I am just getting used to clip list pedals, and the Look CX6 pedals came with my used bike that I just purchased. I then bought Shemano no shoes and the correct clips and all seems to be working reasonably fine.

I am wondering what the dial on the back of the pedals or four. The bike is a 2009 vintage and I'm guessing the pedals date to that time or before.

Also, the left pedal seems a little harder to disengage than the right I really do not want to break my neck fighting to release the clips as I learned how to use them correctly.

The dial on the backside is to chnage from float to no float.
On the top of the pedal is a srew to adjust the spring tension.

As paulkal said, the dial changes degree of float (how much you can rotate your foot when clipped in). Probably it has range that includes at least zero, 3, 6 and 9 degrees of float.

Most likely the reason its harder to disengage from one pedal than the other is becase you need to adjust the spring tension using the screw on top of the pedal that paulkal mentions. I expect there are arrows around the screw pointing which way to turn to increase or decrease tension.