What is colloquially meant by 'chemicals'? I usually take it to mean 'a substance with a name that I don't understand and that I think isn't natural and that I

What is colloquially meant by 'chemicals'? I usually take it to mean 'a substance with a name that I don't understand and that I think isn't natural and that I want to imply is not good for you' and there is no definition beyond that. It is perfectly reasonable to point out that this is irrational.