Mountain bikes are fun because they have so many gears that if you put it in the lowest gear, you can easily ride up a hill. It may take you all day, but you can do it.
It's been a long time since the "10-speed" bike was the pinnacle of gearing technology for bikes. You can get bikes with up to 27 speeds these days, especially mountain bikes.
Why do we need all these gears? Simply put, they let you keep your pedalling speed the same whether you're going uphill, downhill, or across country.
But the main reason mountain bikes have so many gears is to help you get up those steep hills.
The most important thing to remember about shifting is that you must always shift while pedalling.
Front Derailleur
There are two parts to each gear. The gear shifter on the left hand side controls the three chain rings in the front. This is why that gear shifter has three numbers: to let you choose which of the three front rings your chain will rest on. Attached to the gear shifter is a "derailleur," which moves the chain from one ring to another.
When the chain is on (1) the smallest of these three chain rings, it is very easy to pedal. The granny gear is what you call this. The second chain ring is for level, off-road riding (2), and the third, or biggest, chain ring is good for riding on pavement.
So you can definitely use just those three gears if you want to. But if you use the right hand shifter, you can use the small steps of gears that are available.
Rear Derailleur
Depending on how many "speeds" you have, the back chain ring is a cog set with seven, eight, or nine cogs (21, 24 or 27). Each cog is a different size, and again, the smaller cogs will make it very easy to pedal, but you won't go very fast. The larger cogs, on the other hand, will let you go farther with each push of the pedal.
Practice, practise, practise is the best thing to do. Take your bike to a parking lot or somewhere else where you won't be bothered by people and switch from one gear to the next. This will help you get used to each gear and how easy or hard it is to pedal in that gear.
If you're new to biking, you might be nervous about changing gears. Shifting was always a little hard in the "old days," when you only had a pair of center-mounted levers to work with. But now, with twist-type gear shifters, shifting is so easy that you don't have to be afraid of it. Again, you won't hurt the gears if you keep pedalling while you change them.
