The Linux man-pages project -online resources / manual pages - sections / etc

Look here to find these beauties: https://www.kernel.org/doc/man-pages/
The Linux man-pages project documents the Linux kernel and
C library interfaces that are employed by user-space programs. With respect to the C library, the primary focus is the GNUC library (glibc),
although, where known, documentation of variations on other C libraries available for Linux is also included.

The man-pages project provides manual pages in the following sections:

1: User command; man-pages includes a very few Section 1 pages that document programs
supplied by the GNU C library.
2: System calls documents the system
calls provided by the Linux kernel.
3: Library functions documents the functions provided by the standard C library.
4: Devices documents details of various devices, most of which reside in /dev.
5: Files describes various file formats, and includes proc(5),
which documents the /proc file system.
7: Overviews, conventions, and miscellaneous.
8: Superuser and system administration command; man-pages includes a very few Section
8 pages, mainly documenting programs supplied by the GNU C library.