Download the example from this video here: github.com/qVi...
The viewport meta tag was introduced in HTML5. It gives access to web developers to change the way browser looks at device sizes and adjust is rendering of the web pages within the browser window.
The viewport opens a lot of avenues for web designers to layout their websites with responsiveness in mind and should be the first step on the responsive web design journey.
the viewport meta tag is unfortunately overlooked by many coders when they're starting their journey - and only later, when they're mystified why their media queries aren't working the way that they should, they discover the viewport meta tag. This simple standard tag that should have been part of their kitbag all along.