Eubacteria are a large group of prokaryotic microorganisms, commonly known as true bacteria. They are characterized by their simple cell structure, lacking a nucleus and membrane-bound organelles. Eubacteria can be found in various environments, including soil, water, and even inside the human body. They play essential roles in processes like decomposition and nutrient cycling. These organisms can be classified into different categories based on their shape, metabolism, and other characteristics. Some eubacteria are beneficial, such as those used in fermentation and probiotics, while others can cause diseases. Their adaptability makes them crucial for ecological balance.