Instructional media encompasses all the materials and physical means an instructor might use to implement instruction and facilitate students' achievement of instructional objectives. This may include computers, DVDs, CD-ROMs, the Internet, and interactive video conferencing.
Why use Instructional Media? A good aid is like a window, it should not call attention to itself, it should just let the light in. In general, you should use media whenever it can facilitate learning or increase understanding of your material.