The universe contains everything, ever. It is thought to have been created by the "big bang" that somehow broke the laws of physics (made something from nothingness).
The
Earth for example is in the universe.
big bang is thought to have been an explosion (kind of) that was created from nothingness. The explosion was so powerful that the universe is STILL growing today this very second and speaking of size by the way it is thought that the universe is infinite. Or at the very least ridicoulously large. It is estimated to be 14 billion parsecs. A parsec is about 3.26 light years and a light year is how much space light can travel in a year.