Personification is a figure of speech, a form of metaphor. In a personification, something not human is compared to a person. A common cliché is to say 'The lion is the King of the jungle'. Literally, of course, this is nonsense. The lion doesn't tell the other animals what to do; he doesn't collect his wealth from them. But there is a sense in which a simple idea is vividly expressed - the lion is perceived as the strongest, most feared animal in the jungle. (It doesn't matter to readers of creative writing if modern biologists tell us that this is not quite true. It is enough that we understand - and possibly share - the perception that this is how it is.)
The poet Dylan Thomas once wrote, of a hot summer day, that "The sun declared war on the butter; and the butter ran." He is comparing the sun (without saying that it is a comparison, so this is a metaphorical personification) to a great warrior, commander or King; and he is developing the idea by making a pun on the word 'run'. In its literal sense, it means 'melt', but Thomas also uses it metaphorically, as a personification suggesting that the butter is a cowardly person fleeing from the great warrior (the sun).