title: React main entry point
body: <p>I don't understand the structure of most boilerplates out there. I always see 2 files named "index" (one js file and an other html file). I want to understand how the main entry point works. I often see web pack for this job but my main concern is, why do am I using an index.html file when I can (I guess) do all my work in js file?</p>