Okay, imagine you're playing with your toys and your parent is talking to you at the same time. If you want to hear what your parent is saying, you have to focus on their voice and tune out the sounds of your toys. That's a bit like what selective attention is.
Selective attention is when you choose to focus on one thing (like your parent's voice) and ignore other things (like your toys). This helps you pay attention to what's important and filter out distractions.
It's like when you're playing a game and you need to focus on the instructions your friend is giving you. If you don't pay attention, you might miss something important and not know how to play the game.
Sometimes selective attention happens automatically, without us even realizing it. For example, if a loud noise suddenly happens, you'll probably automatically turn your attention to it because it's unusual and could be important.
In short, selective attention is like putting on headphones to listen to your favorite song so you can ignore other noises and focus on what you love.