Okay kiddo, have you ever played with building blocks? Imagine you have a bunch of different colored blocks, like red, blue, and yellow. Each block is different, right? But when you stack them on top of each other, you can make a tower that looks like just one big block! Even though it's made up of lots of little blocks.
Now, imagine that the blocks are actually people. People are all different, with different skin colors, languages, and ways of thinking. But just like the building blocks, we can come together and work together to make something bigger than ourselves.
That's what "that they all may be one" means. It's a kind of wish that people will come together, even if they're different, and work towards a common goal. When we do this, we can achieve things that we never could by ourselves. And it feels really good to be a part of something bigger than ourselves!