As worries about the environmental effects and health hazards of lead continue to develop, lead-free perovskite materials are becoming more and more popular as safer substitutes for conventional lead-based perovskites. This chapter study the fundamental structure, chemical stability, electrical behaviour, and ecological advantages of specific materials to determine what makes them useful. These materials will be arranged primarily according to their chemical composition (including tin, bismuth, antimony, and hybrid organic–inorganic) and structural dimensions (from 0 to 3D configurations). Understanding how lead-free perovskites differ from their conventional counterparts is crucial. These differences directly affect their performance in real-world applications, including solar cells, LED displays, and other sensors. Although recent studies have demonstrated encouraging advancements in lead-free perovskites, several obstacles still need to be overcome before they can be used as viable substitutes for lead-based materials. This chapter lays the groundwork for comprehending these remarkable materials and prepares the reader for the following chapter in depth examination of their particular applications. The aim is elucidating the clear picture of the current state of the discipline and the research challenges.