This document summarizes key concepts related to drug design. It begins by defining what drugs are and how they are classified based on pharmacological effects, drug action, chemical structure, and molecular targets. It then defines drug design as the logical effort to rationally design drugs to minimize trial and error. The main types of drug design discussed are ligand-based and structure-based drug design. The concepts of prodrugs and soft drugs are introduced, where prodrugs are inactive derivatives that are metabolized into the active drug and soft drugs are designed to reduce side effects by minimizing systemic toxicity. Examples are provided for each major topic.