I'm quoting this:

- Gas is the way that fees are calculated
- The fees are still paid in ether, though, which is different from gas

You can read more about it in detail here: https://ethereum.stackexchange.com/questions/3/what-is-meant-by-the-term-gas


Addressing your second question:
They are called wei, finney, szabo etc. (http://ethdocs.org/en/latest/ether.html)


And here's a converter for it: https://converter.murkin.me