This is the official manual for the latest Org-mode release.
The title of the exported document is taken from the special line
#+TITLE: This is the title of the document
If this line does not exist, the title will be the name of the file associated to buffer, without extension, or the buffer name.
If you are exporting only a subtree by marking is as the region, the heading
of the subtree will become the title of the document. If the subtree has a
EXPORT_TITLE, that will take precedence.