The Earth is a planet that goes round the Sun. There are other planets, their satellites, asteroids and comets that go round the Sun. All of them together are known as the Solar System. But our Sun is only one among the millions of stars that are revolving round a common centre. This group of stars is called a galaxy.
Actually there are millions of galaxies. Many of the stars are bigger and brighter than our Sun. Some of them may even have a planetary system like our solar system. Our galaxy, which is called the Milky Way, has a diameter of about 100,000 Light Years. One light year is the distance light can travel in a year, which is about 6,000,000,000,000 miles. So the diameter is 100,000 times this distance. And it has been seen that all galaxies are fast moving away from each other; in other words, the universe is expanding.
Below Universe info from Wikipedia (Read More):-
The Universe comprises everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term Universe may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world or Nature.
Current interpretations of astronomical observations indicate that the age of the Universe is 13.73 (± 0.12) billion years,[1] and that the diameter of the observable Universe is at least 93 billion light years, or 8.80 × 1026 metres.
http://en.wikipedia.org/wiki/Universe
