Fungi can be found more or less everywhere: in soil, water (both fresh- and saltwater), the air, and even on and inside of other organisms. Scientists don’t agree on how many fungi species might exist. About 120 000 of them have been described and an estimate from 2017 predicts between 2.2 and 3.8 million existing species.
The fungi comprises an enormous variety of organisms, fulfilling crucial tasks for the functioning of ecosystems. Fungi play an essential role in the nutrient cycling in ecosystems as decomposers (saprotrophic fungi). They also play an important ecological role as mutual partners (mutualistic fungi) or as parasites on other organisms (parasitic fungi).
For us humans, fungi have a large economical impact. They are used both in food production (e.g. brewing, baking, cheese production, edible mushroom farming) and for the production of antibiotics (penicillin saved enormous numbers of people). On the other hand, as crop parasites they can cause large economical losses, and many fungi can cause of illnesses.