Hello Adyl.
Glad to know u bought a car. Enjoy it!
Twin-Cam means that the engine has two over-head cam-shafts, one for the inlet valves and one of the exhaust valves.
Cams are the parts that help the engine's inlet/exhaust valves to open and "let-in" the combustable mixture to the cylinders. The exhaust valves, of-course, let out the burnt gases. If u look at the Cam in profile, it has one round/circular edge and one parabolic edge.
FYI: When you (or ur mechanic) is setting the timing on the car, you (or ur mechanic) is actually setting up or tuning the inlet/exhaust vales (thru the cams) to open for the designed period of time so that the correct amount of air-fuel mixture is let-in in the cylinder etc.
You don't need to be worried that u bought a Twin-Cam engine car. Whats to worry? The brakes are good. Just make sure you know your driving limits and drive accordingly. Always keep in mind that this is a small front engine/front wheel drive small FAMILY car, meant for slow speed driving around town. Its not a street racer. It has a slightly higher profile than normal so that it can keep up with the road conditions in pakistan. Although I can see you have changed the wheels/tires (they r not racing slicks I could see that) on the car still there is a limit for everything. Even if it says on the car's speedo that it can do 200 Kph doesn't mean you actually need to do that. Its a good car. It should give you plenty of good and happy miles. Always use ur head when driving! (I'll stop here. Too much lectuing). And keep ur car happy too - by regular maintenance.
Don't go to mechanics who don't know about things and tell u all kind of crap about the car. Did u know that Toyota has beaten the record (of Volkswagen Type-1 which sold 21 million cars worldwide, while production continued) by selling more than 25 million Corolla worldwide? They wouldn't have reached this milestone if they were selling bad Corollas. If you need to know about what ur car's engine technology is, go to this place on Supply Road close to Ahmad-Mohammad filling station. Although its a Honda dealerhip but i know that the guys there know and understand what technology is being used. They should take care of your worries about the engine's technology in ur car. I don't remember their names, but they r three brothers and if u can catch hold of the senior one (he is a mechanical engr) he can explain this stuff to you nicely.
Howz abbottabad? I miss the place.
Happy driving. Be safe and enjoy ur car for lots of miles.
Salams,
MSKHAN
P.S: Plz always buckle-up when u drive!