Okay, I was reading my science textbook and here's what happened.

I was doing my final lesson (Science) and read 'In Fact, it is the most common solid substance on earth' as 'In fact, it is the most common substance on earth.' so I started questioning it since I though Air was. When I brought it up to my mom, she didn't think that air was a substance, leading to me looking up what a substance was. (Btw, google's definition of substance and matter is a paradox since they mention each other in the definitions.) I looked up if Air was a substance after that and found a site where it questioned if it was a pure substance (When I was just looking if it was any type of substance.). I scrolled down to see in the 'People also ask' section, 'What type of substance is air?'.  The first sentence said 'Air is nothing but a mixture of a variety of gases.' (My mom earlier said the air wasn't a gas.). Still, have yet to figure out if the air is a substance.

I brought this up onto discord and Snow said that air was a mixture of CO2 (Cardon Dioxide) and Oxygen with small bits of gases mixed into it as well.