How to insert a line break or new line in Markdown?

To insert a line break or new line, you have to type two spaces at the end of a line and hit return once.

Markdown HTML Output
This is the first line of a paragraph.  
This is the second line of a paragraph.  
And this is the third line of a paragraph.
				
<p>This is the first line of a paragraph.<br />This is the second line of a paragraph.<br />And this is the third line of a paragraph.</p>