what is the --save after npm install code example

Example 1: file-saver npm

var FileSaver = require('file-saver');var blob = new Blob(["Hello, world!"], {type: "text/plain;charset=utf-8"});FileSaver.saveAs(blob, "hello world.txt");

Example 2: file-saver npm

import { saveAs } from 'file-saver';