Lyman-alpha emitters are a type of galaxy that emit high levels of Lyman-alpha radiation, which is a specific type of ultraviolet light. These galaxies are important for studying the early universe and the formation of galaxies, as they are often found at high redshifts and are thought to be some of the first galaxies to form after the Big Bang. Researchers study Lyman-alpha emitters to better understand the processes of galaxy formation, star formation, and the evolution of the universe.