Question

What is a streamlined shape? How is it useful?

Answer 1

A body is said to be streamlined if it's shape offers the least possible resistance to a current of air, water or other fluid.A streamlined design is typically a long ellipse tapering to a point in the direction of flow

Answer 2

A streamlined body is the one which is pointed at the ends and broad at the middle. Such body when travel through a fluid or gaseous medium, exhibit minimum friction or resistance. Eg. Body of fish is streamlined to move easily through water.
it helps to reduce the friction .
A body shape which is streamlined helps cut against the friction created by the medium around the moving body.