This is heading 2

This is heading 3

This is heading 4

This is heading 5
This is heading 6 - The least importance

paragraph

This paragraph contains a lot of lines in the source code, but the browser ignores it.

This paragraph contains a lot of spaces in the source code, but the browser ignores it.

The number of lines in a paragraph depends on the size of the browser window. If you resize the browser window, the number of lines in this paragraph will change.

em vs i, strong vs b

The visual result is, by default, the same. 
Both tags emphasis and italic render its content in italics. 
Both tags strong emphasis and bold render its content in bold.

But the semantic meaning is different 
The <em> tag represents stress emphasis of its contents, while the <i> tag represents text that is set off from the normal prose. 
And similar to <strong> and <b>

quotes

This a long quotations For 50 years, WWF has been protecting the future of nature. The world's leading conservation organization, WWF works in 100 countries and is supported by 1.2 million members in the United States and close to 5 million globally. 
can nested some short quote

This is a short quotations 

preformatted

Text in a pre element is displayed in a fixed-width font, and it preserves both      spaces and line breaks

abbreviations

The HTML <abbr> element represents an abbreviation and optionally provides a full description for it. 
Demo below 
The WHO was founded in 1948.

address

Demo using <address> tag to display address

Written by Jon Doe.
Visit us at:
Example.com
Box 564, Disneyland
USA

citation

The Scream by Edward Munch. Painted in 1893.

Some Format - Text element demo

heading

This is heading 1 - The most importance