Educational technology refers to the systematic application of organized knowledge and skills to instruction, as opposed to educational media or audiovisual aids. It involves designing, implementing, and evaluating the teaching and learning process based on research in human learning and communication. Educational media are communication tools used for educational purposes besides the teacher, such as instructional machines and materials that promote learning. Audiovisual media, technology, and aids emphasize the senses of hearing and seeing but have subtle differences in emphasis on the use of tools, design, and instruction.