Everything is a chemical.
All of what we call things are made of atoms. A chemical is just something made of atoms.
But to stop there would be to ignore the common use of the term chemical, which is used to mean something made by chemists, as opposed to something found in nature.
So while water is a chemical, and vodka is a mixture of chemicals, neither is considered a “chemical” by people who lack an understanding of chemistry. Rubbing alcohol, a mixture very much like vodka, but even more poisonous, is generally considered to be a chemical by such people, even if the distinctions are hard to understand.
So gasoline may or may not be considered a chemical by people who don’t understand chemistry. But the additives that are in the gasoline to make it work better are all considered chemicals.
To many people, chemicals are anything listed in an ingredients label that they don’t understand, or that smells unusual. The acid that they put into their swimming pools is a chemical, but the same acid they produce in their stomachs to digest food is not.
So the things in everyday life that are considered chemicals are generally those substances we use to clean, to disinfect, to prevent spoilage, to color, to glue, or to medicate.
Sometimes whether we call something a chemical depends on how we use it. If ethanol is in paint thinner, it is a chemical. If the same ethanol is in whisky, it is not a chemical. If sodium chloride is in your shampoo, it is a chemical. On your potato chips, it is not.