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If you live on Earth, you probably have an address that you can tell other people to inform them where you live. It probably sounds something like 5 Smith Street, ImaginaryTowne MA, 03843, right?
Our cosmic address is a lot longer than that! Our earth is located in a group of planets that is commonly referred to as the solar system. Our solar system is one of millions of other solar systems in the Milky Way galaxy. The Milky Way galaxy is part of the Local Group of galaxies, which is itself located in the Virgo Cluster of galaxies. The Virgo Cluster is located in the Laniakea Supercluster...and so on! The universe practically stretches beyond the boundaries of our imagination, and scientists are still working to describe even the smallest parts of it. So for now, let's focus on our cosmic 'street': the solar system.
The Earth is our cosmic 'house'. We live on a 'street' with seven (formerly eight) other 'houses'. However, our 'house' is the only one that is occupied; the rest have no other humanoid organisms residing in them - as far as we know, at least. Down the road, there is a 'power plant' which supplies all the houses with energy.
In scientific terms, this 'house' is a planet, and there are seven other planets in our cosmic 'street', the solar system. The 'power plant' is our Sun, a yellow dwarf star that provides solar energy to all the planets, but most importantly our planet - there would be no life on Earth without the sun! Our position as the third planet from the sun is also crucial to life; if we were a little too close or a little too far away from the sun, the conditions would not be acceptable for what we know as Earth life.
The eight planets on the block (well, the solar system) are, in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune (and formerly Pluto). They can be divided up into two categories: terrestrial planets and gas giants.
The terrestrial planets are Mercury, Venus, Earth, and Mars. Their status as 'terrestrial' refers to the fact that they are composed mostly of silicate rock and/or metal. In other words, they have solid planetary surfaces; we could theoretically (though perhaps not successfully) land rovers on any of their surfaces (see: the Mars Rover Curiosity).
The gas giants, on the other hand, are composed mostly of hydrogen, helium, and water existing in various physical states. You could NOT land a rover on one of these planets. Planets with this status are Jupiter, Saturn, Uranus, and Neptune. Gas giants are typically much larger than terrestrial planets; for example, Jupiter, the largest planet in our solar system, could fit a little over a thousand Earths inside of it!
These two groups of planets are separated by the Asteroid Belt; in our street analogy, this is equivalent to a fence that is very dangerous to climb over! The Asteroid Belt consists of millions of irregularly shaped chunks of space rock (also called minor planets) - asteroids - orbiting the sun along with the rest of the planets. It only took one of these asteroids to wipe out the dinosaurs 65 million years ago!
Our 'street' may seem very small - after all, it only has eight 'houses'. However, our 'city', the Milky Way galaxy, has been estimaed to contain tens of billions of solar systems. Ten billion streets? That's a lot! And it doesn't stop there. That's only our 'city'! How about our 'state', our 'region', our 'country', and our 'continent'? Imagine how many more 'houses' and 'streets' there must be altogether. When you think about it that way, it makes you realize that our entire human civilization only lives on one 'house' on one small 'street' in a world that practically extends to infinity.