You should never use this hint. This is not documented for a reason. If you would like to use it, this would be documented.
As far as I know, there are cases when the optimizer generates plans differently when optimizing recursive SQL statements. This hint is meant to influence this. Actually, if you are not an Oracle developer who has a conversation with a group of optimizers, why some of your recursive SQL statements do not generate the plans you expect, or you are an open SR developer with Oracle support who is tasked with using this hint to get around the optimizer error, you are almost certainly better off ignoring this and any other undocumented hints that you encounter.
If you really need more information, you can take a look at MOS ID 398605.1, which has links to several related errors.