What are microorganisms, and why are they called microbes?

Microorganisms are tiny living organisms that cannot be seen with the naked eye. They are called microbes due to their minuscule size. These organisms include bacteria, fungi, protozoa, some algae, and viruses. Microbes play crucial roles in various ecosystems, participating in processes like decomposition, nitrogen fixation, and disease causation.
Viruses, although microscopic, differ from other microorganisms as they reproduce only within host cells. Common ailments like cold, flu, and cough, along with serious diseases such as polio and chickenpox, are caused by viruses. Protozoa cause diseases like dysentery and malaria, while bacterial diseases include typhoid and tuberculosis.