Paragraph marks and line breaks, What's the difference?

The keystrokes described below are typical but are configurable within the HTML editor, so may differ for your implementation.

A Paragraph mark is entered into the editor by pressing enter, it adds a <p> to the HTML code.

There is a paragraph mark between this text and the previous "paragraph".

A line break is entered into the editor by holding down the shift key whilst pressing enter, it adds a <br /> to the HTML code.
There is a line break between this text and the previous "sentence".