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 is derived from the first non-empty, non-comment line in the buffer. If no such line exists, or if you have turned off exporting of the text before the first headline (see below), the title will be the file name without extension.
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.