Difference between av preamplifier and amplifier and reciever

This question might have been asked a lot but,can someone explain the difference between avpreamplifier,amplifier and reciever.I am looking to upgrade and Ihear alot about equipment like arcam, adcom,outlaw,rotel,NAD etc. I stopped at magnolia and they showed me the Pioneer elite VSX 74 TXi.Nice unit but, before I buy something I want to veiw all the other options out there.I heard this is a great site to get answers so please let me hear what you have to say.I would like ton know if there are any problems with any products to stay away from. Thanks Paul

An AV pre-amplifier (also called pre-amp/processor, pre/pro, or surround processor) contains audio and video switching and audio processing (which includes converting digital audio to analog, processing digital signals such as Dolby Digital and DTS, time delay for each output channel to reflect different speaker distances from the listening position, bass management, and such). A processor like this does not include amplification to drive the speakers. An amplifier is a component that solely accepts an input signal (or as many as seven input signals) and amplifies the signal(s) to drive speaker(s). A receiver cmobines the features of a processor in the same chassis as an amplifier. Direct examples from Outlaw's product line would be:
- processor: Model 990
- multi-channel amplifier: Model 7125
- monoblock (single channel) amplifier: Model 2200
- receiver: Model 1070