ROTOR makes a lot of chainrings, so it can get confusing! But the differences here can be explained pretty easily.
Here are the ROTOR DM (Direct Mount) rings:
These are a one-piece chainring design that saves weight while simultaneously increasing rigidity. Compared to a standard chainring with spider and bolts, the ROTOR DM ring is approximately 30 grams lighter by comparison. In addition, because the ring is made from a single piece of aluminum, rigidity is improved.
Here are the ROTOR 110×4 rings:
These are traditional 2-piece rings with a spider that bolts to the rings. The advantage to the 110×4 chainrings is they allow you to more affordably change your chainring sizes in the future. For example, you can purchase new rings (keeping the ALDHU spider) for as low as $144, vs. $215 for a new set of DM rings.