The term punctum is also used in the
art world -- most typically
photography, as its first use in this
context is most often attributed to
Roland Barthes in his essay on photography,
Camera Lucida
Punctum refers to that quality of an artistic work that is immediate, salient and demanding. It is what grabs your attention and stirs your emotions. It is how you fall in love with a book, or a painting or a song. To Barthes, "It is this element which rises from the scene, shoots out of it like an arrow, and pierces me."
Contrast to studium: that which is not particularly stirring at first glance, but is appreciated at an intellectual level over time and consideration of an artistic piece.