Meta-commentary: as a term of art in the sphere of employment law, “right to work” is intentionally confusing to laypersons. That was one of the points of the legislation that established the concept: make people who don’t bother with doing research judge the book by its cover, as it were, in the interest of suppressing union activity.
Edit: I am frankly surprised to not see Ohio on that list.
In these states, if a union has presence in a workplace, you are not required to be a member of that union to be employed there. This can mean that your compensation, benefits, work hours, overtime availability, rest hours, safety considerations, etc., are different from (read: worse than) the union member next to you doing the exact same work.
Obviously, the employer isn't going to make those things too much worse, else they would drive more of their workers into the union, which means that even non-union workers in a workplace where a union operates benefit from that union, and they receive that benefit for free.