What is a patent publication? When is the patent published?

All the applications for patent, except the applications prejudicial to the defence of India or abandoned due to non-filing of complete specification within 12 months after filing the provisional or withdrawn within 15 months of applying, are published in the Patent Office Journal just after 18 months from the date of filing of the application or the date of priority whichever is earlier. The patent applications are not open for public inspection before publication. The applicant gets provisional rights in the invention from the date of publication.