JSON streaming is a way to send a lot of information to someone's computer or phone without having to wait for it all to arrive before showing it to them. Imagine you're eating a piece of pizza that's too big to fit in your mouth. You could take tiny bites and chew each one before you can swallow, or you could take a big bite and "chew" as you swallow it. JSON streaming is like that big bite of pizza - you start sending a big chunk of information right away, and it gets sent bit by bit, so the other person can start using it quickly.
In computer terms, JSON is a way of writing down information that can be sent between computers. It looks like a bunch of text with lots of brackets and curly braces. When you want to send a lot of information to someone using JSON, you could send it all at once, but if it's a lot of information, it might take a long time for it all to arrive. Instead, JSON streaming sends the information piece by piece, like taking a big bite of pizza. Since the data arrives piece by piece, the computer on the receiving end doesn't need to wait for all of the data before it starts processing it. This allows for much faster communication between computers.
JSON streaming isn't always the best way to send data, it works best when you're sending a lot of data in one go, and you don't want the person receiving it to wait too long before they can use it.