Json and strings in javascript

There are some functions which confuses me a lot. What is a json? How is it transferred in the Internet? What’s a string? How to read?

So this is a json in javascript.

var love_json = { heart: "🖤", love: "💓" }

This is a string that looks like json.

var love_string = '{ "heart": "🖤", "love": "💓" }'