From JGK's first link: "Pharmacology is not synonymous with pharmacy, which is the name used for a profession, though in common usage the two terms are confused at times. Pharmacology deals with how drugs interact within biological systems to affect function. It is the study of drugs, of the reactions of the body and drug on each other, the sources of drugs, their nature, and their properties. In contrast, pharmacy is a biomedical science concerned with preparation, dispensing, dosage, and the safe and effective use of medicines."
That's about as layman as it gets.