I have often had to explain to clients and potential clients what “at-will employment” means. Briefly, it means that an employer can fire you (in an at-will state, like North Carolina) for no reason, or for any reason, so long as it’s not a reason specifically forbidden by law.
That is the flip-side of your ability to quit your job without notice, without having to give a reason, and without penalty. (Contrary to a common misconception, you have no obligation under the law to give two weeks’ notice, though you could have an agreement to do so with your employer.) I often gave the example of your boss deciding she didn’t like the orange hat you wore into work that day.
Apparently, that also goes for orange shirts….