Difference between .js and .scripts

Hi guys,

I'm new with mix and I have a hard time with understanding difference between building file with mix.scripts and using require in mix.js.

mix.scripts([
        'resources/assets/vendor/jquery/jquery.min.js',
        'resources/assets/vendor/extra/extra1.min.js',
        'resources/assets/vendor/extra/extra2.min.js',
    ], 'public/js/app.js')

this would work perfect but if I create app.js with require() for all this 3 file and use mix.js() it wont work. Whats the difference between combining scripts with "mix.scripts" and "mix.js"? Where I could learn more about building stuff with singe mix.js() instead of lists of scripts?