The tentacle-like structure on some cells is referred to as a pseudopod or flagellum, depending on the context. Pseudopodia are temporary, cytoplasmic projections that are commonly seen in cells like amebas and aid in movement and engulfing food particles through a process called phagocytosis. On the other hand, flagella are long, whip-like appendages primarily used by motile cells, such as sperm, to propel themselves through fluids. Both structures showcase the dynamic adaptations of cells to their environments and functions within biological systems.