A single-speed bicycle is a type of bike that has only one gear ratio, meaning it does not have multiple gears to shift between. This design simplifies the riding experience, making it easier to maintain and operate. Riders can focus on pedaling without worrying about changing gears, which is especially beneficial for flat terrains. These bicycles are often lightweight and ideal for urban commuting or casual rides. They are popular among city cyclists due to their straightforward mechanics and lower maintenance needs. However, they may not be suitable for hilly areas, where multiple gears can provide better performance.