Okay, imagine you have a magic bottle that helps you grow tiny plants. But, just like how you need to give plants the right food, these tiny plants need special food too! That's where a roux culture bottle comes in.
The roux culture bottle is basically a fancy pot that helps you make the special food for your tiny plants. To make this food, you need a special mix of nutrients and sugars. You can't just mix them together in any old pot though, because the mix needs to be sterilized first. This means all the bad germs need to be killed so only good ones are left.
Once the mix is sterilized, you can add a tiny bit of the good bacteria called Roux - this is a special bacteria that loves to eat the mix and grow in it. So, when you add the Roux to the mix, it starts to eat and multiply, making more and more of the special food that your tiny plants need!
So now you can take some of that special food and give it to your tiny plants. And, when they grow big and strong, they'll make you really happy because you helped them grow with the roux culture bottle!