Cute lips are often characterized by their fullness, symmetry, and a slight pout. The corners of the lips should reach out far enough that a line drawn straight up would line up directly with the pupils, according to the Divine Proportion, a principle used by artists for centuries to describe ideal proportions for beauty.
In addition to volume and symmetry, the color and texture of lips also contribute to their perceived cuteness. Lips that are naturally rosy or pink are often seen as more attractive. Soft, smooth lips that are well-hydrated are also considered more appealing.
Ultimately, what makes lips cute is subjective and can vary from person to person. However, these general characteristics are often associated with cuteness.