Anatomy of the Web
What is a website?
A website is simply a collection of HTML documents hosted on the world wide web. Neat. It can be as simple or as complicated as you'd like.What is a browser?
A browser is a program that reads and converts those HTML, CSS, and JavaScript files into something you and me can read and see.
Why should I care about a browser right now?
Well, you use one! And other people may use different ones. There are a lot of browsers out there, but the ones we will care about for now are Chromium (Google Chrome), Safari, and Firefox.
As a beginner, you should be aware of what browser you use and what browser your website supports. 99% of the time, your site will support all browsers! Yay! But sometimes, complicated CSS or JavaScript will have varied support. On your travels around the personal web, you may see a notice on some websites that will tell you "This website only supports chromium for all features", or something to that effect.
Don't stress too much about browser support. It's likely that everything you want to do at this point is supported by every browser! Just wanted to bring it to your attention.