gender and workplace

In my opinion, something that if not everyone, probably many people have faced in their workplaces is the inequality and the gap that exists between men and women and not even to think about the other personalities that are unique. So what are the reasons and how the stereotypes that the society has affect the skills, the opportunities and the abilities that all people have? Why the wages have to differ from person to person because of the gender ? How can we contribute to these situations and maybe to change it?