A collection of the stars, gases and dust is known as a galaxy.
Milky Way is a galaxy to which our solar system belongs.
The shape of the milky way is spiral.
In a galaxy which has a spiral shape, the gases, dust, and stars are organized in such a way that they form a bulge or a disk in the center with spiral arms surrounding it.
Thus the structure of the milky way is best described by the statement - a core with spiral arms.
