Many cell types bear hairlike structures called cilia and flagella from their free surfaces. These structures are extensions of the cell surface and are bounded by the cell membrane. There is no definite morphological or physiological distinctions between cilia and flagella, and sometimes the two terms are used interchangeably. Generally the term cilium is used when the extension is shorter than the cell, while the longer structure is called the flagellum. Cilia are generally more numerous than flagella. Cilia are rather stiff while, flagella have an undulatory motion. Cilia and flagella are widely distributed in both the animal and plant kingdom.
CILIA:these are small hair like projections of cell membrane which are adapted as a locomotory organ in some small unicellular microorganisms.e.g.paramecium.
FLAGELLA:it is the long tail like projection of cell membrane which is adapted as a locomotory organ in unicellular microorganisms like euglena.
They are motile (moving) hairs composed of microtubules.