There are two types of sexual harassment in the workplace: "quid pro quo" harassment and "hostile environment" harassment.

"Quid pro quo" harassment occurs when an employer specifically asks (or strongly suggests) that a person must provide sex acts in order to get some job-related benefit. 

Hostile environment harassment occurs when an employer creates, or permits, offensive behavior in the workplace.  This could be sexually offensive jokes, e-mails, inappropriate touching of employees, and similar behavior.   In order to sue, this behavior must be “severe and pervasive”. A single comment is not be enough to justify a lawsuit. 

In order to file a lawsuit, either (a) the harassing behavior must be committed directly by management, or (b) management must know about it, have had an opportunity to stop it and failed to do so.