How to find what the fields in ls -l mean

At the end of the manual page for the GNU coreutils implementation of ls (as found on Linux systems, and some other Unices):

SEE ALSO
       Full documentation at: <http://www.gnu.org/software/coreutils/ls>
       or available locally via: info '(coreutils) ls invocation'

Following the link to the online manual, one sees a section labelled "What information is listed", which amongst other things describes the long output format in greater detail.

On most other systems, the ls manual is self-contained and describes the long format. For example the OpenBSD ls(1) manual.

Whatever Unix you are on, the ls manual will hold the information you require, or it will refer to the relevant other manual or on-line document that holds the details. If it does not, you should report this as a documentation bug.

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Googling for what an option to a command does is hazardous, as many commands have non-standard extensions that could well be implemented differently in different Unices, or even differently depending what version of the tool happens to be installed. What you'd want to do is to read the manual on your system.

If the manual is not describing exactly what an option does, or what a format is, either explicitly or by reference to some other documentation, then, as I said above, this would be considered a documentation bug.

My ls man page gives me complete information about the Long Format. I guess this must be same on all systems. Scroll down, maybe you will find all the information you need

The Long Format

If the -l option is given, the following information is displayed for each file: file mode, number of links, owner name, group name, number of bytes in the file, abbreviated month, day-of-month file was last modified, hour file last modified, minute file last modified, and the pathname. In addition, for each directory whose contents are displayed, the total number of 512-byte blocks used by the files in the directory is displayed on a line by itself, immediately before the information for the files in the directory. If the file or directory has extended attributes, the permissions field printed by the -l option is followed by a '@' character. Otherwise, if the file or directory has extended security information (such as an access control list), the permissions field printed by the -l option is followed by a '+' character.

If the modification time of the file is more than 6 months in the past or future, then the year of the last modification is displayed in place of the hour and minute fields.

If the owner or group names are not a known user or group name, or the -n option is given, the numeric ID's are displayed.

If the file is a character special or block special file, the major and minor device numbers for the file are displayed in the size field. If the file is a symbolic link, the pathname of the linked-to file is preceded by '->'.

The file mode printed under the -l option consists of the entry type, owner permissions, and group permissions. The entry type character describes the type of file, as follows:

• b Block special file.
• c Character special file.
• d Directory.
• l Symbolic link.
• s Socket link.
• p FIFO.
• - Regular file.

The next three fields are three characters each: owner permissions, group permissions, and other permissions. Each field has three character positions:

1. If r, the file is readable; if -, it is not readable.
2. If w, the file is writable; if -, it is not writable.

3. The first of the following that applies:

   • S If in the owner permissions, the file is not executable and set-user-ID mode is set. If in the group permissions, the file is not executable and set-group-ID mode is set.

   • s If in the owner permissions, the file is executable and set-user-ID mode is set. If in the group permissions, the file is executable and setgroup-ID mode is set.

   • x The file is executable or the directory is searchable.

   • - The file is neither readable, writable, executable, nor set-user-ID nor set-group-ID mode, nor sticky. (See below.)

   These next two apply only to the third character in the last group (other permissions).

   • T The sticky bit is set (mode 1000), but not execute or search permission. (See chmod(1) or sticky(8).)

   • t The sticky bit is set (mode 1000), and is searchable or executable. (See chmod(1) or sticky(8).)

Consider using the info command, as in info ls. Many commands have much more detailed documentation here than in the man pages. In this case, you'll get an offline version of the same documentation in the link in @Kusalananda's answer. You can use info -k <search term> to search the info pages.

Another way of finding help is the apropos <search term> command, which searches the titles and descriptions of man pages to help you find what you're looking for. This helps you find all the sections of a man page, which in the case of ls on my system, is sections 1 (the default) and 1p. man 1p ls has information on the format of the output.