Arrays have methods that extract or modify parts of an array:

slice(start, end) returns a new array from start index up to (but not including) end
splice(start, deleteCount, ...items) modifies the original array by removing or adding items

splice can be a bit more complicated:

It deletes the amount of items specified by deleteCount, starting at and including the start index.
Then it inserts any additional items passed after deleteCount (optional, as represented by the ...items).

let numbers = [1, 2, 3, 4, 5];

// slice does NOT change the original array
let part = numbers.slice(1, 4);
console.log(part);     // [2, 3, 4]
console.log(numbers);  // [1, 2, 3, 4, 5]

// splice DOES change the original array
numbers.splice(1, 2);  // remove 2 items starting at index 1
console.log(numbers);  // [1, 4, 5]

// splice can also insert items
numbers.splice(1, 0, 2, 3); // at index 1, delete 0 items, and insert 2 and 3
console.log(numbers);       // [1, 2, 3, 4, 5]

✅ Key points:

Use slice to copy part of an array without changing it.
Use splice to remove and/or insert items, changing the original array.
Both are very useful for managing array data.

JavaScript Fundamentals