One of the great things about bicycling is its diversity. Bikes come in a staggering array of shapes, sizes and colors. Each design has a specific function. The fun and satisfaction you get from cycling will depend on your picking the right bike for your needs.

Think about what it is you want out of cycling before you visit a bike shop. Do you want to ride fast and on paved roads only? Or will you venture onto dirt roads? Perhaps you just want something you can take to the beach? Here's a look at the most popular types of bikes on the market today.

MOUNTAIN BIKES

Fifteen years ago, the mountain bike was the new kid on the bicycle block. Now mountain bike sales outnumber all other bikes sales combined. The mountain bike is quickly becoming the definition of what a bike is. Rugged and versatile, mountain bikes have 18-24 gears, use high-tech materials for sturdy yet lightweight frames, ride on fat, knobby tires, and feature a comfortable upright riding position and easy to use controls. Many now come with suspension forks and rear shocks for greater comfort and control in off-road riding.

Mountain bikes are great for trail riding, off-road excursions, and rugged touring. They can be ridden on virtually any type of terrain or surface. Minimal maintenance, maximum durability, and an unmatched fun factor make mountain bikes the best way to explore off-road. They can also be ridden in the cities and on streets, though they are slower on pavement and heavier than some other types of bikes.

Due to the popularity of mountain biking, the sport has grown to include several sub-categories. At your local bike shop you can probably find a "downhill" mountain bike, with full suspension and high gearing. As their name implies, they are great for going downhill, but their specialized geometry makes going uphill virtually impossible. You may also find "cross-country" bikes, which are mostly hardtails (no rear suspension). At the higher price spectrum, front and rear suspension can be found. These bikes are built to be light and strong and are the most popular mountain bike out today. The newest type of mountain bike is a combination of the "downhill" and "cross country" and may be called a "freeride," "DualSport" or simply a long-travel dual suspension bike. While not quite as efficient going up the hill as a hardtail, the long-travel dual-suspension bikes are more comfortable going down the hill and make longer, epic rides more comfortable and sometimes more fun.

Less expensive bikes that look a lot like a mountain bike because of their upright position and fat tires - called ATBs or city bikes - are excellent general-purpose bikes, but are not equipped with the specially designed wide-range gearing and powerful brakes that enable a true mountain bike to tackle the really steep hills. ATBs usually have much heavier frames and wheels, as well, which makes them more difficult to pedal off-road.

CROSS BIKES

Perfect for fitness exercising, city biking, commuting, light trail riding, touring and cruising, the versatile cross bike offers an upright riding position for comfort and a sturdy frame for durability. A close cousin to the mountain bike, cross bikes feature tires which are skinnier than mountain bike tires, but bigger than road bike tires. What it lacks in durability for hard-core off-road use, it makes up for in lighter weight for faster road riding. With 18-24 gears, the cross bike doesn't usually have as wide a range as a mountain bike, but provides more and lower gears than a road bike. The frame geometry is somewhere in-between a road and mountain bike, and usually closer to a mountain bike, making them very stable yet also very responsive. For this reason they are becoming very popular as touring bikes.

Cross bikes can be found in almost all configurations. On average, they cost about the same as low to mid-priced mountain bikes, but because of their versatility, some manufacturers are making them with high-tech frame materials and upper-end components. Some are even coming with lightweight front suspension forks. The cross bike is the ultimate aggressive recreational road bike, with the ability to take on groomed dirt roads and light trail riding as well.

ROAD BIKES

Road riders are considered the "purists" of the sport. This is the traditional bike of European road racing, and has a history of nearly 100 years. Road bikes give up quite a bit in comfort, but gain efficiency in top speed. Road bikes feature drop handlebars, skinny tires, 12-21 gears, and require a stretched-out riding position. The frame geometry is typically very tight, making the handling quick and responsive.

For high-speed street riding, these are the bikes. For road racing, high-performance training, triathlons, and long mileage single-day rides, the road bike is your most efficient tool. If the terrain you want to ride on is rough or less than perfect, consider a different bike: the skinny wheels are susceptible to punctures and damage, and while the frame is strong enough for road riding, it won't last long under off-road use.

TOURING BIKES

Built for the long haul, touring bikes look a lot like road bikes but are more comfortable and durable. Not that they're overly heavy or slow. In fact, they're great for day rides and extended trips. They typically have 18-24 gears, with wide range gearing like that of a cross bike. They are more stable than road bikes, and usually come with bigger tires and more powerful cantilever brakes like those found on mountain bikes. This is because touring bikes are required to carry additional camping and other equipment, so stability and braking power is vital. Traditional drop handlebars give the rider an aerodynamic position for long days in the saddle. The bikes also usually have mounts for you to put racks and bags on for long-distance touring or for commuting.

Touring bikes are a great choice for the rider who wants the efficiency and road riding performance of a road bike, but also wants a broader range of gearing and a more comfortable riding position. The touring bike is for riders who like the traditional look and feel of drop handlebars, but who also want a somewhat less temperamental and more versatile bike than the conventional road bike.

OTHER BIKES

Most bike shops carry some more specialized bikes which don't fit into the categories mentioned above. Ranging from very inexpensive "beach cruisers" to very expensive tandems, these bikes offer alternatives when a road, touring, mountain or cross bike just won't do.

As the name implies, beach cruisers are designed for leisurely pedaling on bike paths or city streets. Usually a single-speed, five-speed, six-speed or 12-speed, they are big and heavy, but very rugged and very comfortable - although their weight makes them unsuitable for longer distances. Within the last two years the cruiser has undergone a rebirth, and many companies now offer "high-performance" cruisers with lighter frames, better brakes, and internal six and 12-speed gearing systems that make them almost as versatile as cross bikes, but with a fashionable flair.

Tandems are bicycles built for two people. Tandem riding is on the increase, and there are tandems now available for virtually every type of riding, including road, mountain, and touring. Tandems are an excellent choice for couples of disparate riding abilities. If you or your partner is frustrated at always being left behind, then a tandem may be the answer. Some parents find riding a tandem a great way to spend time with their kids.

General lightweights are bikes that include simple single-speed and three-speed bikes. In the last couple of years, bike companies have begun offering specialized commuter or "metro" bikes. Sharing some characteristics of cross and cruiser bikes, these are made for around-town shopping and errand running. Some of these bikes come with fenders, baskets, and lights.