What defines the art movement known as Postimpressionism?

Postimpressionism is characterized by a distinctive emphasis on geometric shapes and distorted forms, distinguishing it from both Impressionism, which focused on capturing momentary effects of light and color, and the subsequent movements that further abstract art. This movement emerged in the late 19th century, where artists sought to build upon the Impressionist techniques while exploring more personal and expressive artistic styles. Prominent figures such as Vincent van Gogh and Paul Cézanne experimented with structure and composition, using color and form to convey deeper feelings and personal perspectives, rather than mere optical realities.

In Postimpressionism, artists didn't shy away from exaggerating shapes or employing bold colors to express emotion, conveying a subjective experience rather than a strictly realistic representation. This departure from realistic portrayal allows for an in-depth exploration of visual structure and form, creating a bridge between the impressionist techniques and the future avenues of abstract art.

Given this context, the focus on geometric shapes and distorted forms reflects the significant shift in artistic intent and methodology that defines Postimpressionism, making it the correct choice.