While there is no exact definition for the term protozoa, it often refers to a unicellular (one cell) heterotrophic (non-plants) protist , such as the amoeba and ciliates.
they allow efficient movement
A protozoan that moves and feeds using pseudopods is known as an amoeba. Amoebas are single-celled organisms that exhibit flexible, blob-like shapes, allowing them to extend their cytoplasm to form temporary projections called pseudopodia. These pseudopods facilitate movement and help the amoeba engulf food particles through a process called phagocytosis. Common examples of amoebas include Amoeba proteus and Entamoeba histolytica.