A bicycle is a human-powered land vehicle with two wheels, which has been popular since its inception in the 18th century. Today, bicycles are a popular choice for exercise and eco-friendly travel.

Bicycles are noiseless, pollution-free, lightweight, simple in structure, affordable, and easy to maintain. They are not only used for transportation but also for physical exercise. However, few people know exactly when the bicycle was invented, who invented it, and its evolution process.

The world's first practical bicycles appeared in the early 19th century. In 1817, a German named Karl Drais invented a wooden two-wheeled bicycle with handlebars in Paris, France. After the bicycle was invented, it quickly became the preferred means of transportation for Europeans at that time. Throughout the 19th century, some Europeans also envisioned ideal bicycle designs.

The structure of a bike can be divided into three main parts:

1. Guidance system: It comprises handlebars, front forks, front axles, wheels, and other components. The rider can change the travel direction and maintain the vehicle's balance by manipulating the handlebars.

2. Drive (transmission or walking) system: It consists of pedals, a centre shaft, a sprocket, a crank, a chain, a flywheel, a rear axle, a rear wheel, and other components.

The pedalling force of the rider's feet is transmitted through the pedals, cranks, sprockets, chains, flywheels, rear axles, and other components, which allows the bicycle to move forward.

3. Braking system: It comprises brake parts, and the rider can control the brake at any time to slow down, stop the bicycle, and ensure driving safety.

There are several types of bicycles:

1. Ordinary bicycle: This is a single-speed bicycle ordinary people use for commuting. The riding posture is standing with bent legs. The advantage of this type of bike is that it is more comfortable and less tiring for long-term riding.

The disadvantage is that the bent-leg posture is not easy to accelerate, and most ordinary bicycle parts use very common elements, making it difficult to reach high speeds.

2. Touring bikes: Touring bikes are developed from ordinary bicycles. They are light, comfortable, and durable. The frame's geometry is based on comfort, stability, and flexibility requirements, and it can adapt to most terrains.

3. Mountain bike: Mountain bikes originated in San Francisco, USA in 1977. They are designed for riding in mountainous areas and are more durable than regular bikes.

4. Folding bicycles: Folding bicycles are designed for easy portability and loading into a car. Generally, a folding bike comprises a frame and riser folding joint. Public transportation means such as railways and aviation in some places allow passengers to carry bicycles that can be folded and bagged.

Cycling has numerous benefits:

1. Develops the brain and improves physical fitness: Cycling is a movement dominated by the opposite side, which can enhance the agility of the nervous system.

2. Helps in weight loss and prolongs life: Cycling is a periodic aerobic exercise that effectively consumes more calories. Long-term adherence can lead to significant weight loss. Cycling is also a kind of exercise that strengthens cardiovascular and cerebrovascular and cardiopulmonary functions.

3. Reduces stress: Regular exercise reduces psychological stress and prevents depression.

The bicycle is a simple and eco-friendly means of transportation that has been around for centuries. Its benefits are numerous, and it is a great way to stay fit and healthy. With so many different types of bicycles available today, there is a bike for everyone.