So... What are Drugs and genetics?

Ok, Ok... So I hear you want to learn about drugs and genetics. Well, first there are these 2 BIG questions. What are drugs? and What are genetics? Well, first let's see drugs. 
Drugs. Simple, you might think. It's just a "plant with some chemicals"... Right? Well, yes and no. If you search the word "Definition of Drug" on Google, this will appear: a medicine or other substance which has a physiological effect when ingested or otherwise introduced into the body (oxford languages), and a Wikipedia page right next to it. And, yes. Medicine pills are drugs. But that's another story. Many drugs are plant-based. Marijuana is plant-based.  Cocaine is plant-based. Tobacco is plant-based and I can go on and on. Do your own research. But, also many contain chemicals such as amino acids tyrosine and phenylalanine that aim for the dopamine section of the brain, which, well releases Dopamine, a chemical that makes you feel happy. It makes you want more. And, as the saying says, too much of, well anything is bad. Even studying! (But you still need to study!(also, another story) And, as time goes by, you take more and more drugs, and if nothing is done, you will probably die. And yes, drugs have a much more based explanation than just "plants and chemicals" but, in the end, it is KIND of that.