Most web chatrooms are public, and everyone sees the conversations going on, but it is easy for individuals to set up private conversations instead of or as well as the public chat.
Some chatrooms are "moderated", which means that a human watches over the chat within them and can eject troublemakers if they see a problem.
The best advice for responsible adults is to talk frequently to young people about their experience of chatting online, getting then to explain what they do and discuss any problems that come up.
Parents may recommend safe chat services or moderated chat rooms, but youngsters will often still opt for other unsafe alternatives.
It is best to choose nicknames that don't make your gender obvious or attract the wrong kind of interest, such as "sexybeast15".
Chats often make heavy use of abbreviations that are hard for outsiders to understand, many of which are also used by people sending text messages on their mobile phones.