What I understand,
Instructional media includes all the materials and substantial resouces that an educator might use to implement instruction and facilitate students' achievement of instructional objectives.
This may include traditional materials such as chalkboards, Printed material (handouts, books, worksheets), display boards, charts, slides, overheads, real objects, and videotape or film, as well newer materials and methods such as computers, real objects or models, DVDs, CD-ROMs, interactive whiteboard, the Internet, and interactive video conferencing etc. It facilitates learning or increase understanding of material and enhances comprehension of the learners.
The common objectives of Instruction Media can be grasping attention, sprouting interest, support learning with living examples and visual elaboration, making a learning environment in class, and it also helps in turning learning an enjoying experience.
As I read somewhere and want to quote here "Tell me and I forget; Show me and I remember; Let me do and I understand".