Personification is used to provide meaningful description.
Personification means that something non-human is described as having human qualities. Here is an example of the road personified:
It wandered along in curves and easy angles, swayed off and up in a pleasant tangent to the top of a small hill, ambled down again between fringes of bee-hung clover, and then cut sidewise across a meadow. (Ch. 1)
This description shows the road being described as if it were actually walking, and taking its time with where it went, not walking in a straight path. It is an appropriate description because it can explain how a road would end up crooked in the first place, and it kind of describes how a person would walk.
Sometimes personification is not as direct.
The rowboat slipped from the bank then, silently, and glided out, tall water grasses whispering away from its sides, releasing it. (Ch. 12)
In this example, the grasses are described as if they are whispering. It is a figurative way of describing the way in which the grasses are rubbing up against the rowboat. It creates a mood for the scene, which is an important one between Winnie and Mr. Tuck, because he is going to explain to her the importance of living one’s life once, not forever.
Another, different method of personification, is in actual descriptions of objects that both compare them to human features and give them human personality, such as when Winnie’s imagination gets the best of her when she sneaks out to rescue Ma Tuck.
The big glass windows here were lidded eyes that didn't care—that barely saw them, barely gave them back reflections. The blacksmith's shop, the mill, the church, the stores, so busy and alive in daylight, were hunched, deserted now, dark piles and shapes without a purpose or a meaning. (Ch. 24)
The windows are compared to eyes, and the stores are compared to hunched people in the beginning of the sentence and then said to have no purpose in the end of the sentence. It is almost as if the personification in Winnie’s mind is breaking down the closer she gets to the jail, because she is getting more and more worried.
Finally, this sentence personifies both the house and the woods.
The house was so proud of itself that you wanted to make a lot of noise as you passed, and maybe even throw a rock or two. But the wood had a sleeping, otherworld appearance that made you want to speak in whispers. (Ch. 1)
The woods are described as having the appearance of sleeping, which is more of indirect personification. In each of these descriptions of the personification is included to describe how people react to what is being described. Both are a mystery to most people.
Along with other types of figurative language, personification can be used to provide description, create a mood, or add detail. In this way, they help develop the theme of the work.