In this video, I want to introduce you to the CSS. CSS is another language that we use to add style to a page. So, HTML is going to build the structure of your page and then CSS you're going to come and add colors or position elements, add backgrounds or even style images. How does it work? So, take for example this set of pages, those are all the same pages, the same HTML but with different CSS. You can see that by changing the CSS, you can actually change the whole page and the whole appearance of the page. Why you want to do that is because if later you decide that your page you want to have, for example, themes or different colors based on the user or you just want to revamp the style of your page, you can do that by only change the CSS without having to touch on the HTML. How does it does it? So, basically we have the selector and the selector is what's going to tell what tag the CSS is going to change. Then inside the selector, we can add all the properties that we want to change and we can add as many properties as we want. So, let's give an example. So imagine that I have this tag there is a paragraph, we have the tag p and then in my page I maybe would show something like this. So, now what I can do is use the selector p in order to select all the paragraphs in my page and I'm going to start with style and change this style. So, I may start for example to add the color and now my paragraph is going to change to red. Another option is to make the font bold. So now, maybe is a title or I want to highlight this section and I can use this technique or this style. I can also add a border around my paragraph. Finally, I can use the padding, and the padding is the distance between the border and the text and I can use that so that the text is not like totally close to the borders. I can keep adding properties as I need until I'm satisfied with the style of my paragraph. Tag selectors are one of the selectors that we have available and we use them when we want to select a tag. So, for example here, I have the tag selector image and I am selecting all the images in my page and then I'm going to start to add style to them. But that's not the only way, there is another selector that is called class selector. To use a class selector you first define the attribute with the name of the class that you want and then you can use that on your CSS. So, because we are using a class, we're going to start with a dot and then in front of it, we're going to put the name of the class. This is going to make sure that the system is going to access all the elements no matter the tag that contains this class. Another option is to use another special attribute called ID. The difference between IDs and class is that, in your page you are supposed to have only one element with the same ID and while classes you can have multiple elements with the same class. Here, it works very similar to the way the class works with the difference that we add a pound in the beginning and then we add the name that we gave to the ID or the name that we give to the element and then again I just can add my styles. Finally, there is another type of tag that is called pseudo tags. In this case, we're going to select elements based in a certain state, and for example here, I have an example where I'm selecting every tag that is a button when there is a mouse over it. So, this means that when my mouse goes over the element, it's going to change some style that I'm going to add here, if my mouse go out is going to go back to the original style. So, this is away to highlight for example a button or things that you have on the screen, so the user know that he or she can interact with that information. So, keep in mind that CSS is very powerful and they are much more than just the selectors that I showed, and but you can use it to style your page, and you can change dramatically how your page looks like by changing just the CSS. So, keep all the structure on the HTML and then you can use CSS to style your page.