Although the sitter's identity is not verified, he is possibly Johann Dorsch, a cleric in Nuremberg. The clergyman's ardor, spiritual zeal, and intense determination are communicated through the turn of the head, the fixed, staring eyes, and the tight, compressed lips.
With great respect for reality, Dürer has recorded every detail of the man's appearance regardless of how small or unimportant it may be: the wrinkles and lines of the face, the individual strands of fine hair, the coarse skin texture, and even the reflection of window panes in the irises of the eyes. This incisive clarity and accuracy derive in large part from Dürer's experience in the graphic arts.
The portrait is of further interest for having been painted on parchment rather than on wood, which was still the most common support. Experimenting with techniques and materials, Dürer also used silk and linen at times. The animal skin gives the paint surface a fine, smooth quality and lends amazing richness to the oil colors.
More information on this painting can be found in the Gallery publication German Paintings of the Fifteenth through Seventeenth Centuries, which is available as a free PDF https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/german-painting-fifteenth-through-seventeenth-centuries.pdf