The uses of the noble gases depend on their properties. Three useful properties are inertness (they do not react), low density, and being non-flammable (they do not burn).
Helium has a very low density, much lower than air, so a helium balloon floats. Hydrogen is also less dense than air, but it is flammable and can catch fire. Helium is non-flammable, so it is the safer gas for filling balloons and airships.
Argon is inert. A filament lamp has a thin metal filament that gets very hot. In air it would react with oxygen and burn away, so the bulb is filled with argon instead. Argon is also used in welding. It surrounds the hot metal, which stops the metal forming a metal oxide with oxygen in the air.