Ok kiddo, let me break it down for you.
You know what numbers are, right? Like 1, 2, 3, 4, 5...well, mathematicians like to play with different kinds of numbers too. They have something called groupoids which are like numbers that can tell you about how things relate to each other.
For example, if you have three friends named John, Sarah, and Tim, you can make a groupoid by writing down all the different ways they can be in a group together. So you might have John and Sarah, John and Tim, or Sarah and Tim.
Now, the cool thing is you can use these groupoids to do math! Just like you can use numbers to add and subtract, you can use groupoids to do something called groupoid algebra.
Groupoid algebra is like a special kind of math where you can combine different groupoids together to make new ones. It's kind of like mixing colors - if you mix blue and yellow, you get green, right? Well, with groupoids, if you combine the groupoid of John and Sarah with the groupoid of Sarah and Tim, you get a new groupoid that shows how all three friends can be in a group together.
So that's basically what groupoid algebra is - using special "numbers" called groupoids to do math and figure out how things relate to each other. It's like building with blocks - you can build something new by combining different blocks together!