A bicycle frame is the main structure that supports all other components of a bicycle, including the wheels, handlebars, and seat. It is typically made from materials like aluminum, steel, carbon fiber, or titanium, each offering different benefits in terms of weight, strength, and cost. The design of the frame affects the bike's performance, handling, and comfort. Frames come in various styles, such as road, mountain, and hybrid, each tailored for specific riding conditions. The geometry of the frame, including angles and lengths, influences how the bike feels while riding. Proper frame size is crucial for comfort and efficiency, ensuring that the rider can maintain a good posture.