intro - introduction to file formats
Section 5 of the manual describes various file formats and protocols, and the corresponding C structures, if any.
Look at the header of the manual page source for the author(s) and copyright conditions. Note that these can be different from page to page!
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.