This is the official manual for the latest Org-mode release.
To create a link from one Org file to another, you would use something like
‘[[file:foo.org][The foo]]’ or simply ‘file:foo.org.’
(see Hyperlinks). When published, this link becomes a link to
foo.html. You can thus interlink the pages of your "org web" project
and the links will work as expected when you publish them to HTML. If you
also publish the Org source file and want to link to it, use an
link instead of a
file: link, because
file: links are converted
to link to the corresponding html file.
You may also link to related files, such as images. Provided you are careful with relative file names, and provided you have also configured Org to upload the related files, these links will work too. See Complex example, for an example of this usage.