It is a sensory branch of the maxillary nerve (CN V2) that passes through the pterygopalatine ganglion (without synapsing) and then through the sphenopalatine foramen to enter the nasal cavity, and finally out of the nasal cavity through the incisive canal and then the incisive fossa to enter the hard palate.

It provides sensory innervation to the posteroinferior part of the nasal septum, and gingiva just posterior to the upper incisor teeth.

[4][better source needed] It then passes through the hard palate by descending through the incisive canal to reach the roof of the mouth.

[2] The nasopalatine nerve provides sensory innervation to the posteroinferior portion of the nasal septum,[1]: 496  and the anterior-most portion of the hard palate[1]: 370  (i.e. the gingiva[1]: 496 /mucous membrane of the palate[citation needed] just posterior to the upper incisors[1]: 496 ).

This article incorporates text in the public domain from page 893 of the 20th edition of Gray's Anatomy (1918)