Racing bike frames are very often made of carbon: this material is known and appreciated by many cyclists for being extremely light, rigid and comfortable where needed, allowing creative designs and aerodynamic shapes without sacrificing weight and stability. However, it is expensive and less robust than metals such as aluminum.
Choosing a carbon racing bike frame therefore means guaranteeing excellent performance: it is a rigid material when needed, but at the same time guarantees the absorption of vibrations.
In short, with carbon it is possible to combine rigidity and comfort, two apparently opposite characteristics, in a surprising weight!