Sexual harassment may be verbal (like making comments about someone), but it doesn't have to be spoken. Bullies may use technology to harass someone sexually (like sending inappropriate text messages, pictures, or videos). Sometimes sexual harassment can even get physical when someone tries to kiss or touch someone that does not want to be touched.
Sexual harassment doesn't just happen to girls. Boys can harass girls, but girls also can harass guys, guys may harass other guys, and girls may harass other girls. Sexual harassment isn't limited to people of the same age, either. Adults sometimes sexually harass young people (and, occasionally, teens may harass adults, though that's pretty rare). But most of the time, when sexual harassment happens to teens, it's being done by people in the same age group.
Sexual harassment and bullying are very similar — they both involve unwelcome or unwanted sexual comments, attention, or physical contact. So why call one thing by two different names?
Sometimes schools and other places use one term or the other for legal reasons. For instance, a school document may use the term "bullying" to describe what's against school policy, while a law might use the term "harassment" to define what's against the law. Some behaviors might be against school policy and also against the law.
For the person who is being targeted, though, it doesn't make much difference if something is called bullying or harassment. This kind of behavior is upsetting no matter what it's called. Like anyone who's being bullied, people who are sexually harassed can feel threatened and scared and experience a great deal of emotional stress.