Category "shallow-copy"

Does Spread Syntax create a shallow copy or a deep copy?

I am extremely confused for days now regarding the true definition of a shallow copy and a deep copy. When I read the mdn docs (https://developer.mozilla.org/en

JS: Does Object.assign() create deep copy or shallow copy

I just came across this concept of var copy = Object.assign({}, originalObject); which creates a copy of original object into the "copy" object. However, my