what is the function or why do exactly does it do or why many people put it in their cars what is it for??
Cold air is denser than warm air, and a car will run better with denser air. The cold air intake system uses air from outside the engine compartment to run the engine, because the air inside is warmed by the engine. That's the abridged version; Hope that helps.
Riding a bike uses muscles differently than most other activities. It isn't surprising to be sore after a long ride, particularly after a first long ride. It is good to take breaks and go for a short walk every hour or hour and a half or so.
it shouldnt take too much leg effort to use the rear brake/shifter. Your legs WILL get tired if you have proper riding technique (gripping the fuel tank with your knees/thighs, while keeping arms and hands loose). do some squats, man, and enjoy the ride!
takes air from outside of the engine bay. This air is colder and therfore denser allowing more oxygen into the engine, this improves power and efficiency of the engine. Many people have it because they are super easy to put on, cost only a few hundred dollars, and people think they make a bigger difference than they actually do. Unless you cars intake is poorly designed you are only going to gain a couple % on the performance versus just dropping a performance air filter into the stock intake. There are much better ways to get better power and efficiency for a few hundred dollars.
Colder Air More HP/TQ. And add an aftermarket mass air flow sensor you can add from anywhere from 10-30 extra HP easy with the combo setup. And it only takes maybe half hour to an hour depending on how mechanically inclined you are. Plug if you plan on adding some aftermarket parts on your vehical adding a cold air intake is a must so you always have enough cooler air flow coming in. More air + more fuel More power.