What meaning the dash in array when iterating an array in for of loop with entries iterator?

If I normally use for of loop and use iterator as entries that situation look like this:

var a = ['a', 'b', 'c'];
var iterator = a.entries();

for (let e of iterator) {
  console.log(e);
}
// [0, 'a']
// [1, 'b']
// [2, 'c']

iterator: will be the entire array that contain all elements key/value pair. Key will be the index.

e: will be an element in the array

BUT what is this??????

let text = "A A A";
let splitwords = text.split(" ");
let words = [];
for (const [, item] of splitwords.entries()) {
  words.push(item.split(""));
}

console.log(`This is the words: ${words}`);

what meaning the [, item] part???

and why should i use this pattern?

text.split(“”) do exactly same thing or not?

(Otherwise I try solve an text animation problem and this inherit from that code:

framer motion text animation )

Thank you