This may serve to answer your question, and then beat the answer to a bloody pulp, but here it is anyway...

The 950 is a pre-amplifier/processor (and tuner, but they decided the label under the model number was getting too long and left "tuner" off). The idea behind a pre/pro is to separate the different tasks typically handled by a receiver -- move the bulky and power-intensive amplification to an amplifier and let the pre/pro handle only the signal switching and digital processing. There are a number of reasons behind it, typically sound quality (until recently, there weren't any receivers with amp sections that could hold a candle to a good amp or with "brains" that could match a good pre/pro -- there are a handful around now, but they can cost almost as much as a pre/pro and amp combined) and ease in upgrading (the amp should not care about the release of a new surround sound format or a new type of audio or video interface where the pre/pro would become "outdated").

So that's what pre/pros are. What does the 950 do? It controls what source you are listening to and/or watching (DVD, cable, digital cable, satellite, CD, tape deck, VCR, mini-disc, whatever). It also takes care of housekeeping tasks like decoding digital audio from DVD or other sources (digital cable, satellite, HDTV decoder) -- Dolby Digital, Dolby Digital EX, DTS, DTS ES, Dolby Pro Logic II if it is a two-channel format, etc. There is also work like bass management -- if your speakers can't reproduce sound below, say, 60Hz, the 950 would re-direct the info from those speakers that falls below 60Hz to the subwoofer. When it's through with all of that sort of work, it then delivers the selected video signal (if you chose to use it this way) to your TV, the LFE signal to the subwoofer (if necessary), and the separate analog audio signals to the amplifier(s) which then boost the signals and send them on to the speakers. In the case of the powered speakers Matthew Hill and I mentioned, each speaker would have it's own built-in amp, so the 95 would feed unamplified signals to each speaker directly, but as I said that's fairly unusual.

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Gonk