Explanation

Explains how or why something happens.

Features:

starts by naming the topic
describes items related to the topic in their right order
explains how the items relate to each other and to the topic
may end with a concluding statement
may include visual images, e.g. flowcharts and diagrams, which support what is written in words
written in the present tense.
Examples:

the life cycle of a butterfly
how gears work
labelled diagrams
flowcharts.