In our state they mean the same thing. It is how our employment laws are setup, and how the state department of labor treats the issue. I've fought many a case for my union, and also for me in these instances, and I'm pretty familiar with the way it "was". Laws change, I couldn't be sure it is all the same now, of course.

I suppose it is all in the perspective - you have the right to work, so you can leave anytime you want and still have the right to go find work elsewhere without punishment. I'm sure the right to fire was a compromise to placate the employers, but they can't black list an employee that was let go without cause on paper. Few want to put it to paper, because that just gives the lawyers ammunition to use tort relief.