They are overly confident with themselves and they often exaggerate their achievements and they usually think they are better at their job than they actually are. They negotiate for higher salaries than women and it is often said that they never take the first offer on the table, a mistake that women usually make. A mistake that is partly responsible for the pay disparities between men and women.
Studies show that women doubt themselves too much and that we generally tend to undersell our values and skills in the job market. We are often unsure and uncertain in a way men aren't. Even with external validation and career success, a woman must somehow always wonder if she is good enough. That contrast isn't surprising. It exists in our programming. The one that has been instilled in both genders since the beginning of time.