Understanding Lorentz Force & its Helical Motion

[EdTheHead]

I'm having a bit of trouble understanding what exactly the lorentz force is. In this diagram here
[PLAIN]http://img7.imageshack.us/img7/7065/helicinbfld.jpg
I know its the force that's keeping the proton in that helicoidal trajectory so I can see its perpendicular to the direction of the magnetic field but what exactly is it. I know that the proton is exerting an electric field as well as a magnetic field since its in motion but I don't know what it is that causes this helicoidal motion is it the interaction between the magnetic field of the proton between the magnetic field its entering or is there more to is than that?

 

[Doc Al]

The Lorentz force law describes how electric and magnetic fields exert forces on charged particles. In this case, the magnetic field exerts a force that is always perpendicular to the velocity of the moving charge, thus creating a radial acceleration.

See: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html#c2"