Archaebacteria are a group of single-celled microorganisms that are distinct from both bacteria and eukaryotes. They thrive in extreme environments, such as hot springs, salt lakes, and deep-sea vents, where most other life forms cannot survive. Their unique cell membranes and metabolic pathways allow them to adapt to these harsh conditions. Unlike typical bacteria, archaea have different genetic and biochemical properties. They can be classified into several groups, including methanogens, which produce methane, and halophiles, which thrive in high-salt environments. These organisms play essential roles in their ecosystems and contribute to biogeochemical cycles.