Semantic HTML is writing HTML in a way that it can be read and understood by both people and internet readers or search bots. Correctly written HTML should indicate what each part is relative to the rest of the app.
You're going to write a static webpage using semantic html for a photography website. Your site should include
A header at the top of the page with the name of your photography business
A side navbar (right or left) with links (that don't need to work)
A main content section with pictures you want to display.
A footer with contact information for your business.