Hi fi$hys
I'm glad you asked that question!

There's a little bit of science you need to learn to keep fish successfully, but it's not too hard. At 12 years of age you will be able to understand it easily.
Basically, a tank is said to be cycled when there are enough of the right kind of bacteria in it to consume all the ammonia that the fish produce from their wastes and turn it into nitrItes, which is another chemical. There will also be enough of another kind of bacteria that will eat all the nitrItes and turn them into nitrAtes.
Both ammonia and nitrItes are harmful to the fish, but nitrAtes are not harmful unless there is a whole lot of it in the water. NitrAtes can be easily removed when you do your weekly water changes and tank cleanings.
The bacteria I mentioned can come from the air and will start growing in your tank as soon as the fish are added, so you already have some of them growing in your filter and on your gravel. They will be reproducing as fast as they can because they have lots of food, and you will eventually have enough of them to do the job.
If you know someone who has an established tank, you could ask them for some of their filter material (which will have lots of these Beneficial Bacteria on it) and put it right into your filter to give you a head start and hurry the process. If not, you will just have to do a lot of water changes to keep the harmful chemicals at a minimum. That will keep your fish healthy and safe until your own bacteria grow.
What you are doing is called, "Cycling With Fish." It's called that because when the fish eat, they produce their own ammonia which feeds the bacteria. It's natural and the way many fishkeepers cycle their tanks. I did my original tanks that way too.

These days many people add ammonia from a bottle to their tanks and cycle it before they get their fish. This is called, "Fishless Cycling." In the end both ways do the same thing.
Does this make sense so far?

If not, let me know and I will try to explain more. If so, please post how big your tank is and how long it's been running. I'll then explain how you can test the water to tell how far along in the cycle your tank is.
