This document discusses teaching materials and aids. It begins by explaining that teaching involves communication between a sender, message, and receiver. It then notes an old Chinese proverb that people remember 10% of what they read, 50% of what they see and hear, and over 70% of what they see, hear and do. The document defines teaching materials and aids as tools that supplement classroom instruction to enhance student interest. It describes different types of teaching aids including visual, audio, and audiovisual aids. It provides criteria for choosing effective aids such as accessibility, visibility, practicality, interactivity, and usability. Finally, it discusses strategies for using aids appropriately and why teachers employ aids to stimulate learning and improve understanding.