what are the 2 usefulness of the ear?i mean its ability
Ears have more than two functions. The most obvious purpose of ears is allowing us to hear. The reception and concentration of sound waves and transmission of those vibrations to the areas of the brain where they can be interpreted and given meaning is the primary and most critical use of ears.
Internal parts of the ear are also critical to our sense of balance. Impairment of the functions of the inner ear can greatly impact balance and movement.
It may not be "useful" in the same sense, but ears are also seen as parts of the body that may be decorated with jewelry that may have cultural or personal significance. People who use eyeglasses appreciate having ears to support the bows of those glasses.