What is the universe, according to Christianity?

As the title says, what is "the universe", according to Christianity? The term does not occur in the Bible, making it impossible to address this question through hermeneutics alone. However, many arguments about creation assert that God created it, whatever "it" is. See here for an example. What is it, and what is in it, according to Christianity? If there are different concrete interpretations of what the universe is, what are those arguments or definitions? I am asking for an overview of viewpoints on this subject.