There is no universal method for classifying motorcycles. Still, motorcycles available in the market can be broadly grouped in six major categories - sport, touring, standard, cruiser, dual-purpose, and dirt bike. The classification has been done based on the purpose for which they can be used. The six major categories are broadly put under - Street and Off-road.
The standard motorcycles, also known as naked bikes or roadsters, distinctly stand out due their unique upright riding position. The riding position in these motorcycles is neither too relaxed (as is generally the case of cruiser bikes) or too sporty - forward leaning (as is the case of sports bikes). Ergonomically speaking, the feet and the torso of the rider are almost in the same plane. The handlebars are placed such that the elbow, shoulders and wrist of the rider lie in the same line and they give the rider a more sporty feel as compared to the cruisers.
The engine capacity of motorcycles in this category generally vary from 150cc - 1200cc.
Due to the relaxed riding position that cruisers offer, they are more comfortable to ride when compared with other types of motorcycles. The feet of the riders are placed distinctly forward and the handlebar are high above the elbows. Since the bikes offer a relaxed position for riding, they are generally coupled with engines with more low-end torque. This puts the riders at ease and it does not require them change gears very frequently. These bikes are most suited for short to medium journeys over straight roads since the manuverabilty is greatly limited by the relaxed style of riding position.
Motorcycles in this category generally employ large capacity engines (150cc - 1500cc).
Sports bikes are designed by keeping in mind the characteristics like speed, acceleration and cornering. They offer a very sporty riding position due to the low placed clip-on handlebars and very agile due to the high performance engines that they use. Every component used on such bikes is put keeping while keeping in mind the word 'performance'. The design is done so as to extract maximum output out of everything. Because these motorcycles are expected to achieve higher speeds in comparison to motorcycles in other categories, aerodynamics play a very important role in case for these motorcycles and is an important consideration which the designers keep in mind.
The touring motorcycles are the most comfortable to ride and the riding posture that they offer can be compared to that of the cruisers. Unlike the cruisers, the motorcycles generally have large luggage compartments and can carry almost everything that a rider might require while taking a long journey.
These motorcycles generally have a large windshield that protect the rider from the wind.
Sport touring motorcycles are the combination of sport bikes and touring motorcycles and try offer the best of both. The performance characteristics of these bikes are close to a sports bike and utility tends to be more close to a touring motorcycle. They employ high performance engines like found on a sports bike and have huge luggage space like that is being generally offered on touring bikes. The riding position is less aggressive as compared to a sports bike and is configured more towards the riders comfort due to their intended usage.
In terms of design, they are analogous to a sport touring bike which combine sport and touring. In their offerings, they tend to combine the intent of a naked bike and an off-road bike, therefore, a dual-sport or on/off road motorcycles are combination of naked motorcycles and off-road motorcycles.
The suspension system employed on these bikes allows a good amount of suspension travel because they are expected for off-road use too.
Unlike specialised off-road bikes which are designed specially to achieve one purpose and are not expected to ply on paved roads, these bikes are road legal and can be used for moderate off-roading.
These motorcycles are designed to do just one thing - off-roading. These bikes are employ a special suspension so as to provide long travel under severe shocks. Generally, these bikes use wire spoke rims since they are more forgiving than alloys, are more capable of shock absorption and have less weight in comparison. Since these bikes are subjected to severe shocks during usage, they are built rugged and employ very robust components. Due to their intended usage, they are generally stripped of all essential components (horn, headlights, indicators etc.) that make way on road legal vehicles. This is done with the intention of keeping the weight to the minimum.
When compared to other categories of motorcycles, these bikes tend to employ a small capacity and low-weight engine. This is done so as to keep the total mass of the bike as low as possible since the impact with which a bike hits the ground is greatly affected by the height and mass of the vehicle when it falls freely under the affect of gravity.