Laocoön is not a work by Lessing. It is a sculpture by the Greek artists Agesander, Athenodoros, and Polydorus. Lessing wrote a treatise titled "Laocoön: An Essay on the Limits of Painting and Poetry," in which he analyzed the sculpture and discussed the differences between the two art forms.
Gotthold Ephraim Lessing Knowledge Showdown: Will You Emerge Victorious?