 When you're coding in data science, one of the most important things you can do is be able to work with web data. And if you work with web data, you're going to be working with HTML. Now, in case you're not familiar with it, HTML is what makes the worldwide web go round. What it stands for is hyper text markup language. And if you've never dealt with web pages before, here's a little secret. Web pages are just text. It's just a text document. But it uses tags to define the structure of the document. And a web browser knows what those tags are and it displays them in the right way. So for instance, some of the tags, they look like this, they're in angle brackets, and you have angle bracket and then a beginning tag. So body, then you have the body, the main part of your text. And then you have an angle brackets and a backslash body to let the computer know that you're done with that part. You also have P and backslash P for paragraphs. H one is for header one. And you put it in between that text. TD is for table data or the cell in a table. Any mark it off that way. If you want to see what it looks like, just go to this document DSO three, three, one HTML dot text. I'm going to go to that one right now. Now, depending on what text editor you open this up, it may actually give you the web preview. I've opened it up and text mate. And so it actually is showing the text the way I typed it. I typed this manually, just typed it all in there. And I have HTML to see what a document is. I have an empty header, but that sort of needs to be there. This I say what the body is. And then I have some text, li is for list items. I have headers. This is for a link to a web page. Then I have a small table. And if you want to see what this looks like when it's actually displayed as a web page, we'll just go up here to window and show web preview. This is the same document, but now it's in a browser. And that's how you make a web page. Now, I know this is very fundamental stuff. But the reason this is important is because if you're going to be extracting data from the web, you have to understand how that information is encoded in the web and is going to be an HTML most of the time for a regular web page. Now I will mention something that there's another thing called CSS and web pages use CSS to define the appearance of a document HTML is theoretically there to give the content and CSS gives the appearance and that stands for cascading style sheets. I'm not going to worry about that right now because we're really interested in the content. And now you have the key to being able to read web pages and pull data from web pages for your data science projects. So in sum, first, the web runs on HTML. That's what makes the web pages that are there. HTML defines the page structure and the content that's in the page. And you need to learn how to navigate the tags and the structure in order to get data from the web pages for your data science projects.