The operator norm is a way we measure how big a transformation can be. Imagine you have a toy car and you want to move it from one place to another. You can push it just a little bit, or you can push it very hard so that it goes very far. The operator norm tells us how much force we can use to move the car from one place to another.
In mathematics, we often work with something called a function, which is like a machine that takes in some input and gives out another output. Just like pushing a toy car, we can use a function to transform one thing into another thing.
The operator norm tells us how much we can stretch or squeeze the things we put into a function. For example, imagine we have a function that takes in a vector and gives back another vector. We can use the operator norm to measure how much the function will stretch or shrink the vectors we put into it.
Think of it this way: if we have a big machine that takes in some blocks and squishes them together to make a smaller block, we can use the operator norm to measure how much the machine compresses the blocks.
So, the operator norm is a tool we use to measure how big of a transformation a function can do. Just like we can measure how hard we can push a toy car or how much we can squash some blocks together, we can use the operator norm to measure how much a function can stretch or shrink the things we put into it.