Okay, so imagine Australia is like a giant puzzle piece that fits into the bottom of the world. It's normally a pretty hot and dry place, but sometimes things happen that can make it even hotter and drier or wetter and cooler. One of those things is called the El Niño-Southern Oscillation, which is a really long name that means "the way the ocean and the air move around in a certain way."
When El Niño happens, it means that the water in the Pacific Ocean near Australia gets warmer than usual. This can cause a lot of problems like drought (which means not enough rain) and bushfires (which means big fires that burn up trees and animals). It can also make the air really hot, which is not very fun for people.
But sometimes the opposite happens, and it's called La Niña. This means the water in the Pacific gets cooler than usual, which can cause a lot of rain and flooding. It can also make the air cooler, which is more comfortable for people but can also cause some problems like too much rain that can damage farms and houses.
So basically, the El Niño-Southern Oscillation is a natural thing that can happen in Australia and affect the weather in different ways. It's important to pay attention to it so we can be prepared for any problems that might happen.