Paragraphs are separated by at least one empty line. If you need to enforce a line break within a paragraph, use ‘\\’ at the end of a line.
To keep the line breaks in a region, but otherwise use normal formatting, you can use this construct, which can also be used to format poetry.
#+BEGIN_VERSE Great clouds overhead Tiny black birds rise and fall Snow covers Emacs -- AlexSchroeder #+END_VERSE
When quoting a passage from another document, it is customary to format this as a paragraph that is indented on both the left and the right margin. You can include quotations in Org mode documents like this:
#+BEGIN_QUOTE Everything should be made as simple as possible, but not any simpler -- Albert Einstein #+END_QUOTE
If you would like to center some text, do it like this:
#+BEGIN_CENTER Everything should be made as simple as possible, \\ but not any simpler #+END_CENTER