Simply put, process-art means art that is about making art for the artist. This act of making and the materials has an inherent and often aesthetic value in the final product.
This means that the artist seeks meaning in the substrate, the meaning, and the possibilities of the materials and methods used to make the work of art.
For example, we represent a young abstract painter. To best understand her work, it would be useful to talk about on the materiality, the viscosity, the textures and malleability of oil paints. She derives value or meaning or purpose from the process of painting. Working WITH oil paints is paramount to what she does. While the work of art is beautiful, its beauty in her case is examined though the medium.
If you consider traditional landscape painters: we would communicate more about his background, where he visited, why the locations were significant to represent. In this case, the meaning is less about his materials and more about the final product: a picture of a mountain-scape, tress, wildlife.