Okay, so imagine you have some candy and you want to share it with your friends. But you want to make sure everyone gets the same amount, so you need to divide the candy up in a fair way. This is what rationality is all about - making decisions that are fair and reasonable.
When we talk about rationality in a more grown-up way, we mean using logic and reason to make decisions. This means thinking carefully about all the options and considering the evidence before making a choice. It might mean weighing up the pros and cons or looking at the consequences of different choices.
Being rational also means not just going with your gut instinct or your emotions. Sometimes our feelings can lead us astray and make us make bad decisions. But by being rational, we are using our brains to make the best choices we can.
So, like dividing up your candy, being rational means making fair and thoughtful decisions that are based on evidence and reason.