How does Alice Hoffman use imagery in Practical Magic?

Imagery:

"Night and Day, the aunts called them, and although neither girl laughed at this little joke or found it amusing in the least, they recognized the truth of it, and were able to understand, earlier than most sisters, that the moon is always jealous of the heat of the day, just as the sun always longs for something dark and deep."

"Sally considered her little sister greedy and selfish; Gillian thought of Sally as a prig and a prude, but they were still sisters, and now that they were about to be separated, they stood in front of the open window and hugged each other and cried, then vowed they would be apart for only a short while."