What is helium and why is it used in rockets?

Helium is quite fun, in fact, it's a gas!

No, it's a chemical element as described above. And it's only a gas at higher temperatures. On average in the whole universe, it is liquid or icy solid, because it is usually extremely cold anywhere out there. Helium as a gas is therefore the very very rare exception.

I know quite a bit about helium as I used to work in a helium factory. However, I didn't like the boss and quit - I refuse to be spoken to in that tone!

I refuse to be spoken to in that tone!

Nice one!

Hervé L'EisaSep. 8  07:24 am JST

Helium is quite fun, in fact, it's a gas!

It's a gas gas gas!

And it's safer than hydrogen. Hydrogen burns fiercely, ask the Hindenburg crew. That's why we don't use zeppelins anymore.