Okay kiddo, imagine that there is a big island called Hibernia. But Hibernia isn't just a regular island, it's also a person! That means Hibernia looks and acts like a person, but is still an island.
Whenever we talk about Hibernia, we say things like "she" or "her" instead of "it" because we're referring to her as a person. Hibernia might have a certain personality or characteristics that we associate with her because she's a personification.
So basically, Hibernia is an island that we talk about like a person because it's been given human-like qualities. Cool, huh?