An inert gas is a gas which does not undergo chemical reactions under a set of given conditions. The noble gases often do not react with many substances[1], and were historically referred to as the inert gases. example argon, neon(at normal conditions)
Inert gases do not react with other substances as they have completely filled valence shell and has electronic configuration of ns2np6 .
Therefore they are known as noble gases and belongs to group 18 of periodic table.