Yes. The road bikes and MTBs have multiple gears while the BMX and track bikes only have one.
They have 20 0r 22 gears depending on make...
Yes.
no!!
Yes.
yes
MotoGP bikes have 6 gears.
Depending on the bike yes most adult sized bikes have gears
olympic gears
They make cars and bikes work.
Unfortunately, you can't change gears on bikes in HeartGold.
dirt bikes in the past had less gears and power then dirt bikes have today
yes
Yes in fact i have one they have three gears and neutral but most are automatic
Yes, BMX bikes were used in the 2008 Beijing Olympic and is going to be used in the 2012 London Olympic.
There are internally geared bikes, where all the gears are tucked away inside the hub and then there are externally geared bikes, with a stack of differently sized sprockets on the outside of the hub. Apart from that they're just called gears.
Racing bikes are so different from your conventional bike in many ways. They are made to be a lot lighter than the average bike you see today and are made for speed. Racing bikes are fitted with minimum components the gears can range from 18 gears to 30 gears.