The document discusses the uses of audio-visual aids in teaching. It defines audio-visual aids as instructional materials that use both hearing and sight to convey concepts to students. The document outlines several principles for the proper use of teaching aids, such as supplementing classroom teaching and using aids that stimulate student thinking. It also describes different types of audio, visual, and audio-visual aids including blackboards, bulletin boards, film projectors, and gives examples like television, mobile phones, laptops and computers. The advantages of aids are that they draw student attention, bring concrete examples, and make lessons more effective.