What is the Universe?
The Universe consists mostly of what we consider Space. Space is rightly named because Space has more space than anyone can even imagine. Not only that, but more and more Space is coming into existence or rather, into nothingness. The Universe isn't just empty space. The Universe also consists of all the stars, galaxies, nebulae, space clouds, and all other celestial being. Every living thing, every particle, every atom is part of the universe. To put it in terms that are easier to understand, the 'system', which tends to be our earth, or our city, or just our workplace or house sometimes plus the surroundings, which is anything that you really don't think about all the time, say... our solar system, and our star cluster, and our galaxy, and everything that surrounds our galaxy is what the universe really is.
What is so important about the Universe?
Every night when you look into the sky, and see all those stars, they wouldn't be there if there wasn't a universe. Many things about the planets early life are explained by looking at other planets. Heavy elements, such as gold, are mostly created through one of the most powerful explosions in the Universe, the collision of neutron stars, containing neutron-rich (neutrons being the electrically neutral, subatomic particles.)
Is the Universe really expanding?
NASA has found using the constantly growing distance between our galaxy and other galaxies near our own that the Universe is in fact expanding. Through the use of the Hubble Telescope, close up pictures of other galaxies helps measure their distance from us.
The Universe is Accelerating, too?
Also using the Hubble Telescope, the distance between other galaxies, and Einstein's General Theory of Relativity, scientists have discovered that universe is constantly growing, and growing faster and faster.
Dwindle, Robert: "Universe" 2006