You still haven't answered all my questions. I also asked you to supply a schematic, not just a verbal description of the circuit. Your description doesn't add up, and I don't know that you know what some of the terms mean. For example, do you really mean "common collector"? That's rather unlikely at best.
In general, impedance matching is a way to deal with the problem of having a signal at one impedance but something you want to feed that signal into requires it to be at a different impedance. Since most of the time a lower impedance signal is more useful (resonant circuits and transmission lines being notable exceptions), there are various circuits that try to maintain a signal but make it lower impedance. Such circuits are often referred to as "buffers". Depending on requirements, this can be as simple as a single transistor in emitter follower mode. A opamp with negative input tied to the output is another common buffer. It can get lots more complicated as the requirements get more stringent.
