The document describes the key characteristics of prokaryotes. It states that prokaryotes are single-celled organisms without nuclei or membrane-bound organelles, that they contain circular DNA and sometimes plasmids, and that they can have different shapes, cell walls, and methods of obtaining nutrients like photosynthesis. It also notes that archaea are prokaryotes that lack peptidoglycan in their cell walls, have unusual lipids, and live in extreme environments without using oxygen for respiration.