I see them in multiple places and I need to understand when I use each one
Hello! Have you completed the Semantic HTML modules already? Even if you have, a review of those lessons might be good!
If you need just a quick review on what the different tags are and when to use them, try this short article.
Basically, in very short form,
<div> is a way to section off a web document for styling,
class is an attribute that can be applied to divs or any other element to connect to the CSS for styling, and
<header> are semantic HTML tags that section off a web document in a way that makes the page easier to read and search.
Thank you! Now it is more clear.