Basic elements are the backbone of any HTML document. You will see these elements in the source code for all web pages.

MDN HTML element reference

The Absolute Basics | Table of Contents

Questions

Display a message. I would suggest "Hello, world!" if you want to follow tradition. Use minimal html code.
Display "Hello HTML5" with a HTML5 document type and the HTML root element.
Display several paragraphs on a webpage of text with a HTML5 doctype and HTML root element.
Display several lines of text with spaces, tabs and new lines placed throughout, in a bare-bones document.

Advanced Questions

Write a webpage in 6 major versions of (X)HTML, conforming to the standards of each version. Research these yourself.
Display a message with all HTML code you consider essential.