1. What does final drive ratio mean?
There is a gearset in a car's differential. The ration of those gears is the final drive ration.
2. What are street dampers?
Shock absorbers (aka dampers) that are comfortable to use on the streets, in everyday traffic? Race shocks are firmer and don't offer as comfortable a ride as with softer shocks, but they do offer noticeable performance advantages.
3. If FR means front engine, rear drive, then MR means middle engine, isn't that where the seats are?
Well, you don't see rear seats in a mid-engined car.
4. What's a double wishbone suspension?
One of the types of suspension. Basically, two horisontal A-arms on each side. Most race cars have those, and in open wheel series you can see them easily - F1/CART/IRL, etc.
5. What's a carburetor do? What's it look like?
It provides fuel and air to the engine (and mixes them at a precise ratio). Use google picture search engine to find a picture.
6. How does a carburetor differ from fuel injection systems?
Carburetors are mechanical while injectors are electronic.
7. Why do I always see people with those fat exhaust tips? What's so great about it? Does it increase performance?
For looks. The tip itself adds no performance advantage. Usually the whole exhaust is made bigger to present less restrictions to the airflow, or rather exhaust gas flow, from the engine.