HTML5 gives a document semantic structure or a meaning for the reader.
Semantically well-formed pages provide a high level of user experience, even if it’s about your co-workers or a screen reader. A well structured HTML page will provide visual structure, even if all CSS styles have been disabled. Once you learn to look past element names and think of their essential meaning, it gets a bit easier to write markup. Think of your chunks of content in terms of how they relate to each other and in which contexts they can be used. If you’re ever in doubt, I highly recommend the flowchart of HTML5 sectioning elements to help you along.