Why does NASA use helium?

Why does NASA, the world's leading space agency, rely so heavily on helium? Is it because of helium's unique physical properties that make it indispensable for their missions? Or does NASA have a specific need for helium that other gases cannot fulfill? I'm curious to know, what specific applications does helium have in NASA's operations? Is it used in spacecraft propulsion systems? Or perhaps, does helium play a crucial role in maintaining the integrity of spacecraft structures? I'm eager to understand the reasons behind NASA's choice of helium and the significance it holds in their space exploration endeavors.