Basically, a line break is like hitting the "enter" key when you are writing text. The browser will not go to the next line until it runs out of space, or sees a tag that will force it to the next line. So typing the following in your text editor will display only one line of text in the browser:
Hello,
I want
a new line
This gives us:
Hello, I want a new line

To make the text move to the next line, use your tag from above:
Hello,

I want

a new line

interesant