Let's start here. Pre/pro is a Preamp/Processor. This is a device that switches, processes, and amplifies signals at very low voltage levels. Much like a reciever, only without the amplifier section that power the speakers. A reciever is a pre/pro and an amplifier in one box. When you use separates (as in a preamp in one box and an amp in another), your components are connected to the preamp which outputs signals to the amplifier to power the speakers. If your preamp is also a video processor/switcher, then it will also route video signals to the video outputs and to the TV, projector, or whatever.
An integrated amp is like a receiver, but it lacks a radio tuner and video processing. Integrated amps are also 2-channel (there might be a multi-channel one out there somewhere, but not that I know of).
A 2-channel amp is just an amplifier that takes an input from a preamp or from a preamp output of a reciever and amplifies the signals to power speakers. Two-channel refers to the number of speakers it will power, in this case it has two channels of amplification which means it will power 2 speakers. A monoblock amplifier is an amplifier that only powers one speaker (so a 1-channel amp). Many purists use these amps to achieve the best stereo separation on the electronic level that they can. Since monoblocks are also dedicated to only powering 1 speaker, they often offer more headroom than a normal multi-channel. Many multi-channel amps (such as those made by Bryston and Emotiva) use a number of small monoblock amps in a modular configuration so each amp gets its own transformer, set of capacitors, etc. This yields better relilability, servicability, as well as stereo separation and power performance for each channel.
I hope this helps. Post again if you need more clarification.
