Matrix of ones

Imagine you have a big piece of paper with a bunch of boxes on it. Each box is a spot where you can put a number. Now imagine you fill in every box with the number 1. So every box has a "1" in it.

This big piece of paper with all the "1s" in every box is called a "matrix of ones". It's just a fancy way of saying that you have a bunch of "1s" arranged in a certain pattern on a piece of paper.

You can use this matrix of ones in lots of ways, like to do math problems or to demonstrate certain concepts in math. But the important thing to remember is that it's just a bunch of "1s" in a certain pattern on a piece of paper.