Salary inversion is when someone who does a job is paid less than someone who does a different job but gets paid more. It's like a reverse order: the person who does more work gets less money, and the person who does less work gets more money. For example, a janitor might get paid less than a CEO. This is not fair, because the janitor does a lot of work and deserves to get paid more. The CEO probably isn't doing as much work and isn't making that much of a difference, but they get paid a lot more. So salary inversion is when someone is getting paid too much or not enough compared to someone else.