Final answer:
Cilia are short, hair-like structures that have a wave-like motion and tend to occur in large populations on the cell surface. They are used to move entire cells or substances along the outer surface of the cell.
Step-by-step explanation:
Cilia are short, hair-like structures that are found in large numbers on the cell surface and have a wave-like motion to move through the cell. They are used to move entire cells or substances along the outer surface of the cell. In contrast, flagella are long, hair-like structures that are fewer in number and used to move an entire cell.