|Do Mics really sound different?
Yes. Every mic "colors" the sound in one way or another, much like the way speakers color the sound of your home stereo. Some mics try to be "transparent" but this is not always desirable. With vocals and many instruments, for example, you want a mic with some presence boost for that pro-sounding "sheen".
What is this directional pattern nonsense?
What are you? a Drummer? Then you above all need a uni-directional mic so when close miking they pick of what it is pointing at, not everything in the room, like an omni directional mic does. Cardioid mics are directional because they pick up everything in the heart-shaped pattern in front of the mic. A Bi-directional pattern is also called a "figure 8" pattern cause that is how it looks on a graph. You can record from the front and back but not the sides.
What is Phantom Power?
Condenser mics output a weak signal that must be boosted so the mixer's preamp can boost it further into a useable signal. Some condenser mics use batteries to do this. Other's rely on getting this power from the mixing board. Boards that feature phantom power send a voltage down the mic cable to the mic which is used to amplify the signal there. The signal then arrives at the preamp and is further amped. Dynamic mics do not need phantom power. You can read more in the forums about it and in this article by Shure
What's a -10 pad?
A Pad refers to attenuation, or a lowering of volume, output or loudness. A -10 pad reduces the sensitivity of the microphone by 10 decibels so it can withstand louder sounds like drums, cymbals, screaming vocalists and other awfully loud things. Some mics may have -20 pads or -15 pads. You normally cannot adjust this--its on or off.
What's Bass Roll-off?
Some mics have a switch that cuts the lower bass frequencies that the mic pics up. Why? When you record with a quality microphone you will find there is more bass in your environment than you thought. If you are recording close to an ventilation system vent you will find that even a normal rush of air coming out is enough to make a thundering wind boom. Traffic, railroads, airplanes even if far away can be picked up. Finally, a big problem in the mix is getting rid of unwanted bass. it sometimes makes sense to get rid of it at the source. Many mixers have bass rolloff switches on preamps, so if the mic does not have it it is usually no big deal.