This option enables you to make sure that any non block elements or text nodes are wrapped in block elements. For example <strong>something</strong> will result in output like: <p><strong>something</strong></p>. This option is enabled by default as of 3.0a1.
If you set this option to false it will never produce P tags on enter or automatically it will instead produce BR elements and Shift+Enter will produce a P.
Note that not using P elements as root block can severly cripple the functionality of the editor.
forced_root_block : 'p'