Originally Posted by FBinNY

As others have said most inner tubes are butyl, whether they make a claim about it or not. Butyl is used because it's more impervious to air molecules and so holds air better than other materials while still being strong and stretchy.

Don't let the tone of some of the other responses get to you. None of us, even the most expert, was born with this knowledge and had to learn it at some point in our lives.