ViewPort :

Viewport is the user’s visible area of a web page. This is the part you can see from your device or monitor.
It is located on the (head> tag of the HTML.

(meta name="viewport" content="width=device-width, initial-scale=1">

purpose of a viewport :

A viewport makes sure a site display well on all device (mobile phones, tablets, computers, and even larger screens).
In a nutshell, viewport plays a significant role in designing responsive and mobile-friendly websites.

width:
width property controls the size of the viewport.
In the above example, it is set to equal the device width.

initial-scale:
It controls the zoom level when the webpage is first loaded.