The Milky way is a collection of more than 100 billion stars arranged in a disk-like pattern. The disk has a diamter of about 25,000 pc. This is where most of the gas and dust is. The bulge is only about 3 kpc arcross. Little gas and dust, lots and lots of stars.
Halo is, perhaps a few times larger than disk.
No gas and dust, just stars and star clusters. Disk has spiral arms. Stars in disk move in circular orbits in disk-plane around center. Stars in halo move on elliptical orbits without any one orbital plane. In the region of constellation Sagittarius, highly obscured.