Protozoa are single-celled organisms that belong to the kingdom Protista. They are diverse in form and function, often found in various environments such as soil, freshwater, and marine ecosystems. Protozoa play essential roles in the food web, serving as both predators and prey in their habitats. These microorganisms can be classified into several groups based on their movement and feeding methods. Some, like Amoeba, move using pseudopodia, while others, such as Paramecium, use cilia. Protozoa can be beneficial, aiding in nutrient cycling, or harmful, causing diseases like Malaria in humans.