I need to get 2 different types of microphones for my home AV system. I need permanently installed microphones in a few locations in my home to receive voice commands for my home automation system. I also need a good microphone in my AV room for a karaoke type system. Im not sure what kind of microphone I need for each but I have found most microphones I've looked at are either dynamic microphones or condenser microphones. What is the difference and what type will I need?

Well your best bet is to get a microphone specifically designed for each application. There are other factors to consider other than Dynamic or Condenser type microphone. Basically a dynamic microphone works like a speaker in reverse. A dynamic microphone consists of a cone attached to a coil around a magnet. Sound pressure on the cone moves the coil in relation to the magnet which generates electric signals. A condenser microphone works like a capacitor. It consists of a fixed plate and a thin membrane. sound pressure on the membrane changes the capacitance of the circuit which generates the electrical signal. These are the two basic types of microphones, but you should really chose a microphone based on your intended application. A good quality microphone suitable for voice recording should work great for your AV room. You can find reasonably priced microphone and equipment at Pro Acoustics here:
http://www.proacousticsusa.com/category.php?cId=40

For input of voice commands you should consider a mic designed for this purpose. You will likely be further away from the mic for inputing voice commands and you probably want this microphone to be less conspicuous as well.