Question

What previewing material would accompany an expository text?

Answer 1

An introduction is given about how the topic of interes will be treated.

Usually images of an explanatory nature are included, with a explanatory talk, the images are included to bring the reciver closer to the topic of interest in a friendly way.

it's purpose is to inform a non specialized public, and sometimes, without prior knowledge, so that the same present an interest in the subject.