This document discusses supplementary teaching materials and aids that can be used in addition to course books for teaching English as a foreign language. It notes that supplementary materials may include skills development, grammar, vocabulary and listening practice, as well as authentic sources like newspapers. Both traditional teaching aids like blackboards and newer audio-visual aids can be used to engage students and facilitate learning. Examples given include using audio to develop listening skills, visual aids to improve clarity, and videos to demonstrate processes in an interesting way.