Helium balloons are filled with helium gas, a colorless, odorless, and non-toxic noble gas. Helium is lighter than air, which is why balloons filled with it float. It is commonly used for party decorations, advertising, and entertainment. The popularity of helium balloons can be attributed not only to their buoyancy but also to their safety compared to hydrogen, which is highly flammable. Helium is a finite resource, mainly extracted from natural gas fields, and its use has raised concerns about sustainability and potential depletion in the future.