The ``=pod'' directive does nothing beyond telling the compiler to lay off of through the next ``=cut''. It's useful for adding another paragraph to the doc if you're mixing up code and pod a lot.
Head1 and head2 produce first and second level headings, with the text on the same paragraph as ``=headn'' forming the heading description.
Item, over, and back require a little more explanation: Over starts a section specifically for the generation of a list using =item commands. At the end of your list, use =back to end it. You will probably want to give ``4'' as the number to =over, as some formatters will use this for indentation. This should probably be a default. Note also that there are some basic rules to using =item: don't use them outside of an =over/=back block, use at least one inside an =over/=back block, you don't _have_ to include the =back if the list just runs off the document, and perhaps most importantly, keep the items consistent: either use ``=item *'' for all of them, to produce bullets, or use ``=item 1.'', ``=item 2.'', etc., to produce numbered lists, or use ``=item foo'', ``=item bar'', etc., i.e., things that looks nothing like bullets or numbers. If you start with bullets or numbers, stick with them, as many formatters use the first =item type to decide how to format the list.
And don't forget, when using any command, that that command lasts up until the end of the paragraph, not the line. Hence in the examples below, you can see the blank lines after each command to end its paragraph.
Some examples of lists include:
literal code L
A link (cross reference) to name L manpage L item in manpage L section in other manpage L<"sec"> section in this manpage (the quotes are optional) L"sec"> ditto F Used for filenames X An index entry Z<> A zero-width character
In particular, you can leave things like this verbatim in your text:
Doubtless a few other commands or sequences will need to be added along the way, but I've gotten along surprisingly well with just these.
Note that I'm not at all claiming this to be sufficient for producing a book. I'm just trying to make an idiot-proof common source for nroff, TeX, and other markup languages, as used for online documentation. Translators exist for pod2man (that's for nroff(1) and troff(1)), pod2html, pod2latex, and pod2fm.
If you had not had that blank line there, then the translators wouldn't have seen it.