According to FIDE rules http://www.fide.com/fide/handbook.html?id=174&view=article
there are many differences (read the rules for details), and sometimes titles are awarded regardless of rating, as noted below:
The Award of Titles
Titles may be awarded for specific results in specific Championship events, or are awarded on achieving a rating as laid down in these regulations. Such titles are confirmed by the QC Chairman on advice from the FIDE Office. They are then awarded by FIDE.
Titles are also awarded based on applications with norms with a sufficient number of games. These titles shall be awarded by the General Assembly on recommendation by the QC that the candidate meets the requirements. The Presidential Board or Executive Board may award titles in clear cases only, after consultation with the QC.