Inert gases are gases that don't react with other elements. What this means is that they won't combine with other elements, and trigger chemical reactions. I've posted a picture of the Periodic Table. Take a look at the VERY LAST row, all the way on the RIGHT side of the table. That row is made of up NOBLE GASES (He, Ne, Ar, Kr, etc.) Those noble gases are INERT. They are non-reactive.