2  Here Come Multimedia:  Its Meaning
2.1  Picture (or Image)
Traditional teaching/learning materials are texts.  In the origin/base of a text there are pictures.   But the text is not such a kind of thing that re-presents the pictures.
To reconstruct pictures from a text is a jump - a blind jump.  Indeed, those who can, more or less,  read a text are those who already has the pictures from which the text originates.  ( It is a tough work to describe this coffee cup in the form of text.  And, even if I could finish it, nobody can re-presents this coffee cup  from the text. )
If it is possible to serve pictures directly in the form of picture, that is the best.