Think about Google Maps, Gmail, and other applications that are really highly interactive and yet provide you a great user experience, in a very fast way.
As a Web developer, the browser is one tool that’s really required to know inside out.
If you start from zero, I would recommend you study 2 things:
- What happens when you type a URL in the address bar and press enter
- How to use the Developer Console offered by your browser
That’s a good start.