Optical cavities are structures that confine and enhance the interactions of light within a controlled space. These cavities are typically composed of two or more highly reflective mirrors that create a resonant cavity in which light can bounce back and forth multiple times, leading to increased interaction with the cavity's contents. Optical cavities have a wide range of applications in various fields such as quantum optics, laser physics, and telecommunications. They are used to increase the sensitivity of optical sensors, enhance the generation of high-intensity laser beams, and manipulate the properties of light for quantum information processing. Research in optical cavities focuses on optimizing cavity design, exploring novel materials for mirrors, and investigating new applications for these structures. Overall, optical cavities play a crucial role in advancing optical technologies and enabling new scientific discoveries.