There are a couple of parts of right to work.
You can hire and fire at will. But if you fire, you still have to justify it if the employee tries to collect unemployment. So you can fire someone but you are still on the hook for unemployment compensation if the employee was terminated and it cannot be proved that he didn't violate work rules, etc.
I believe it also prevents labor unions from requiring workers to join the union to work for an empoyer. Consequently an employer can have both union and non-union workers side by side doing the same jobs. It becomes the employees choice as to if he want to be in the union.
I believe that if an employee chooses to join the union, it also gives him the right to only pay the dues that are 'directly related' to collective bargaining. Consequently if the employee does not believe in the political adjenda of the union he is a member of, he does not have to pay the portion of the dues that support political activity (that part may actually be a federal law that applies to all states, but I know it applies to 'right to work' states.