For what is setInterval, I do not understand where and how to use it

Answer 1

x = setInterval(() => {console.log("hi")}, 500)
the code above will logs hi every 500ms

Answer 2

Take a look at this example I did so you can have a better understanding:

https://code.sololearn.com/WtWo50WAHrTt/#js

Answer 3

Generally when creating an animation on your webpage.

it work just like thread in Java.