Imagine you have a toy box filled with different toys, like blocks and balls. Each toy has a certain way it can be played with - blocks can be stacked on top of each other to make towers, and balls can be rolled around.
Now imagine that instead of toys, we have something called operators. Operators are like special instructions that do different things to whatever we're working with. Just like each toy in the toy box has its own way of being played with, each operator has its own way of acting on whatever we're working with.
But what are we working with? In a vertex operator algebra, we're working with something called a vertex operator. Think of the vertex operator as a special kind of toy - one that can interact with other toys in the box in different ways.
So let's say we have two vertex operators. We can combine them to make a new vertex operator using something called a product. Just like if we combine blocks in a certain way, we can make a tower, if we combine vertex operators in a certain way, we can make a new vertex operator.
But what's special about vertex operator algebras is that we can use these vertex operators to describe something called a conformal field theory. This might sound complicated, but think of it like a game where you're trying to move things around on a surface without changing the shape of the surface. Vertex operators help us describe how the things we're moving around interact with each other on this surface.
So, to sum up: vertex operator algebra is like a toy box of special instructions and toys that can interact with each other in different ways. By combining these toys (or vertex operators) in certain ways, we can describe how things move around on a surface without changing its shape.