This document discusses various types of antibiotics and antimicrobial agents. It categorizes them based on their chemical structure, mechanism of action, spectrum of activity, and organisms they target. Some common antibiotics discussed include penicillin, cephalosporins, sulfonamides, tetracyclines, aminoglycosides, and metronidazole. Their mechanisms of action, resistance, uses, and adverse effects are described. The document provides a detailed overview of classification and properties of different antimicrobial drugs.