Drag is also called air friction or fluid friction. It is experienced by all the objects moving. Fluid friction is experienced by all the objects moving in a medium generally liquid(water) is the medium, higher the viscosity higher is the drag offered by the medium. Drag forces depend upon velocity of the object moving through medium.
Objects moving in fluids have streamline shape because this shape reduces the amount of friction experienced by the objects because this shape enables the object to cut and pass through the medium whether it is air or water, the streamline shape is like the shape of bullet it is pointed from forward so that it can cut the medium in front of it and can get pass through it.
Examples – Ship in water, Airplane in air, F1 cars on road these all have streamline shapes.
