We do not have an accurate map of the Galaxy, but guess that it would look similar to other galaxies , that we have seen, if viewed from outside. Note the structure of a disk galaxy. Most of the interstellar matter in the galaxy is in the disk. The disk is rotating, and contains spiral arms , which are concentrations of stars, gas, and dust. The spiral arms are dynamic systems with stars moving through the arms rather than spending all their lives inside or outside an arm.
Spiral arms are sites of star formation and are rich in interstellar matter.
It is hard to determine where the spiral arms are in our galaxy. We have to observe the radio emission from neutral hydrogen atoms in the interstellar medium. The galaxy is held together entirely by gravity. Each star orbits around the center of the galaxy. Stars in the disk all move in the same direction, while the stars in the halo have randomly oriented orbits .