Topic 1: HTML pages are structured through the use of elements
Elements are what we know as the characters inside the angled brackets that we can also refer to as tags. Each element is made of two tags: an opening tag and a closing tag, which ultimately tells the browser about its information. Tags act like containers and knowing what tags are available along with their functions determines the structure of the site in the end.
Topic 2: CSS associates style rules with html elements.
The style rules of CSS govern how the elements of HTML should look and contain two parts: a selector and declaration. Selectors indicate elements and declarations sit inside the curly brackets and indicate how the element selected should be styled through properties and values. This can be done with either external css or internal css.
Topic 3: There are advantages to using external style sheets.
External style sheets simply refers to a seperate CSS page apart from your HTML page. All of your web pages can be linked to the same CSS document, saving time and resulting in less code. For example, if you update or make changes to your CSS, the elements on every HTML page will be updated. Although CSS can appear within an HTML page, it is generally considered good practice to keep your HTML and CSS as separate documents if you are working with a website that has multiple pages.