BDSM includes various scenarios revolving around dominance and submission sometimes expressed through sexual bondage, slave master roles and the intermingling of pain and pleasure.
"Cyber Sex" is a term that was most widely used in the early 90's and while it is most defiantly is still done it has been shortened to "cyber" if it is addressed at all.
Most "cam sites" have a host, usually a girl who is paid credits for her time while she strips.
Most who like to have "cyber sex" want to get off with the help of their imagination and may not want to be made to feel uncomfortable with the thought of being judged on cam.
But "free" adult cam sites (like this one) are actually chat sites with webcam capabilities where the people on cam are not paid.
Roleplay is a popular activity in most adult chat rooms, how seriously it is taken depends on the participants.
As in the real world, not everyone asks to have sex, they simply feel the moment out or know what the expectation is.
While most people have webcams today, many people choose not to use them.