I might mention there is also at-will employment. Some employees get at-will employment & right to work mixed up. In at-will employment (all states, except Montana & in some situations it applies there), you can be terminated at any time for any reason (& generally no reason) except for a reason prohibited by law (such as race, religion, gender...). You're an at-will employee unless you have a binding employment contract or CBA to the contrary.
You also can quit for any reason you like at any time unless you have a binding contract to the contrary.