Topic 1: HTML uses elements to describe the structure of pages.
Each element or tag in HTML will include an opening tag and a closing tag. These tags act as containers that hold your information or text and tell you something about the information. The character inside the bracket tells you what its purpose is. An opening tag character is placed inside brackets and a closing tag character is placed in between brackets with a forward slash in front of the character.
Topic 2: CSS allows you to change the appearance of your HTML
It is helpful to imagine that there is an invisible box around every HTML element when designing with CSS. CSS allows you to create certain rules for each of those elements or blocks, changing the way they look. Block-level elements are the main text inside the tag and inline elements are text housed within the main text. You can change the appearance of the boxes that house the text or the actual text, by changing color or borders or italics or bolds.
Topic 3: CSS properties affect how elements are displayed.
The selector indicates what element this rule applies to while the declaration indicates how the elements referred to in the selector should be styled. Declarations sit inside curly brackets that are made up of a property and a value that is separated by a colon. One declaration can house several different properties. For example, you can assign a typeface and a text color to one selector or element.