The word vial sounds like another word, "vile" (making them homonyms), but they mean completely different things. A vial is just a small glass bottle that contains a chemical or drug. "Vile" is evil.
One of the coolest things about the English language is how specific you can get. For example, got a small glass bottle made for carrying chemicals or drugs? There's a word for that! That word is vial. There are bottles for soda and bottles for beer, but if what you're carrying is drugs, chemicals, or similar substances, you're carrying them in a vial.