I assume, that a) by Halo stars, you mean high velocity stars, and b) by disk stars, you mean stars that stay within the galaxy (Normal stars).

Halo stars are usually very old stars that do no orbit the centre of the Galaxy the same way that our Sun or other stars in a galaxy. Rather, they travel in elliptical orbits, which often take them well outside the plane of the Galaxy.

• Stars in the disk all orbit in the same direction and nearly the same plane, while halo stars have more randomly oriented orbits.

• Clusters of young stars are found only in the disk.

• Disk stars come in a broad range of masses and colors, while halo stars are mostly of low mass and red.

• Gas and dust are abundant in the disk but not in the halo.