Okay kiddo, have you ever heard of tally marks? They are lines we draw to keep track of things, like counting how many times we jump rope or how many cookies we ate.
Well, a tally stick is like a grown-up version of tally marks! Instead of drawing lines on a piece of paper, people in the olden days would make cuts on a sticks to keep track of things like money or possessions.
The stick would be split in half and each person would keep one half. For every transaction, they would make a cut on their half of the stick and the other person would do the same on their half. That way, they could both keep track of the exchange and make sure everything was fair.
Later on, people started writing on the tally sticks instead of just making cuts. They would write down what the transaction was for, how much was exchanged, and who was involved.
Nowadays, tally sticks are not used very much anymore because we have better ways of keeping track of things, like using computers. But they were an important tool for keeping track of important information in the past!