The terms top, bottom, and switch were originally derived by and used for despriptions amongst the gay community to describe roles during sex positioning, particularly among men. A top is a person who penetrates, a bottom is one who receives penetration, and a switch (taken by the gays from the baseball term in reference to a "switch hitter") engages in both activities.
This is generally how I'm used to these terms as well. I don't generally consider "bottoming" to be submitting, but usually just meaning "fucked in the ass." It's very much possible to bottom in that regard, as a Dom, or for a sub to top. Depending on what flavor the Dom is feeling like, should they themselves be "versatile." Switch I've really come across primarily as a kink term, most gay men I know that are willing to be the penetrator or the penetrated refer to themselves as "vers" or "versatile." I think thats mostly a newer term though, if I asked around I'm sure I'd find more who identify as switch and mean top or bottom.