This document summarizes various types of antimicrobials including their classification based on chemical structure and mechanism of action. It describes how antimicrobials work by inhibiting processes like cell wall synthesis or protein synthesis. It also discusses problems that can arise with antimicrobial use like toxicity, hypersensitivity reactions, drug resistance through mutation or gene transfer, and superinfections. Antimicrobials are obtained from fungi, bacteria, and actinomycetes.