There are basically two types of harassment in the workplace. Harassment perpetrated by a manager or supervisor that affects an employment decisions such as hiring or promotion and harassment that interferes with the ability of an employee to his/her work and or creates an intimidating or hostile environment in the workplace.
The first and most commonly recognized form of harassment is Quid Pro Quo harassment. This type of sexual harassment is where a supervisor or manager asks for sexual favors in return for an employment benefit such as a promotion, salary increase, new responsibilities, or time off. This type of harassment could also occur in exchange for not having a negative work benefit happen - such as a demotion or termination. Quid Pro Quo is the most common form of harassment that we see in movies and TV, but it is small of the whole harassment picture.
Hostile Workplace Harassment is where an employee experiences a consistent hostile, intimidating or offensive work environment. This type of environment affects the victims work and emotional well-being. It is important for an employee in this situation to make management and the perpetrators aware of the conduct. If it continues, it may rise to the level of illegal harassment.
Another form of harassment that falls into both Quid Pro Quo and Hostile Workplace Harassment is where putting up with an organization-wide conduct is a prerequisite for employment. An example of this is a female employee in a warehouse who is told to just "put up" with lewd behavior, touching, posters, etc... because that is just how life in a warehouse is and that she should just accept it.
Harassment in whatever form it takes is unacceptable and illegal. It is of upmost importance that organizations have a comprehensive harassment policy and training program for all employees. This is the only way to decrease the instances of harassment and avoid legal issues as a result.