Random lasers are an advanced type of laser device that fundamentally differ from traditional lasers in both concept and operation. They show significant potential for applications in imaging, sensing, and photonic chips due to their unique light field properties, simple design, ease of fabrication, and low cost. Unlike conventional lasers, random lasers rely on disordered structures for optical feedback, resulting in distinctive features such as low spatial coherence and random emission wavelengths and directions. Directionality is crucial in many applications, and integrating random lasers with optical fibers enhances their output directionality while enabling miniaturization and integration. Additionally, metal nanoparticles serve as highly effective scatterers, offering a larger scattering cross-section compared to dielectric nanoparticles of similar size. Their localized surface plasmon resonance further enhances light confinement and significantly boosts optical gain, making them instrumental in the generation of random lasers. This chapter delves into the fundamental concepts, key characteristics, and control mechanisms of random lasers. It also examines design strategies, fabrication techniques, emission properties, and the applications of random lasers with fiber-embedded cavities, providing examples in imaging and sensing. Furthermore, it briefly discusses WGM-coupled random hybrid cavities and their applications in information security.