Cyanobacteria are also known as blue-green algea, it undergoes photosynethic process that is similiar to plants, and can be found in a wide range of aquatic and terrestrial environments. They are ancient forms of bacteria on Earth, playing a vital rule on nitrogen fixiation in ecosystems. It can convert atmospheric nitrogen into ammonia, forming usable organisms to living things. Also, cyanobacteria possess chlorophyll and many other pigments, which gives the blue-green color, and it is capable of living in environemtn such as freshwater, soil, and even extreme conditions. Some common examples of cyanobacteria are anabaena, nostoc, and spirulina. Anabaena is a nitrogen-fixing genus that can be found in freshwater, many are toxic, and it can be detrimental to living things; nostoc also contributes to nitrogen fixation; spirulina is a bacteria that is often used as a dietary supplement because it ocntains sufficient protein.
Source: study.com (cyanobacteria definition, characteristics & types)