Function constructor, IIFE

Question

(function() {})();

const increment = (function () {
return function inr(number, value) {
return number + value;
};
}();

I checked Stack Overflow, and other sites, but am still having trouble understanding.

https://stackoverflow.com/questions/8228281/what-is-the-function-construct-in-javascript

(Please convert this code into relevant python code if possible, I'm comfortable in it)

Answer 1

How is it better than just

increment = lambda number, value: number + value