From B2evolution

[edit] README.html

To provide help for users of your plugin, you should ship with a README.html file.

This file should be a standard HTML file, so it is viewable with any browser. Additionally, you should attach HTML IDs to paragraphs or DIVs which describe your settings.

The format of the IDs is: [plugin_classname]_[setting_name].

So, if you have a setting "foobar" in your plugin "myplugin_plugin" you should use id="myplugin_plugin_foobar" with the paragraph that gives more details on your setting and b2evolution will create a help icon that links to this paragraph next to the setting on the "Edit plugin settings" page.

[edit] Code documentation

You should also use phpdoc comments in your PHP code, to describe the file, class, members and methods.

Please refer to http://manual.phpdoc.org/ for details.