I didn't get the part of the "meta tag". Could anyone explain it to me please?.. thanks :)

When you use the (meta name="viewport" content="width=device-width, initial-scale=1"), you're telling the browser what size actually is your viewport. In fact, you could use a fixed width like 800px. But, what you want to do for your site to adapt the media size, is to tell the browser that the viewport width is the size of the browser (width=device-width).

If you don't put the meta tag in your html, your website design will kind of squeeze into the viewport without replacing all your elements as declared in your css @media (width=).

I'm not sure if I explained it well...

Earlier in the course he talked about how it's best to use "relative units" instead of exact. Percentages instead of exact pixels, so I assume this was one was kinda had to put two and two together with haha