What is Area 51 and what makes it famous?

Area 51 is a facility in Nevada operated by the United States government. The origin of the name is unknown. It's believed its primary purpose is to develop and test aircraft and weapons. However, in recent years and decades, Area 51 has become famous and synonymous in pop culture with conspiracy theories, especially ones involving UFOs. It requires extremely high levels of government clearance to access Area 51. Thus, the mystery of its operations still remains.