This is an entry in our Disneyland 101 Glossary: Disneyland Resort definitions in under 101 words, from Mouse Brief.
Direct-to-Room Service is the option for Disneyland Resort Hotel guests to check-in to their rooms online, or through the Disneyland app, and then access their room with a digital key. The service is called “direct-to-room,” because guests can go straight to their available room without stopping at the front desk.
If you wish to use this service, we recommend becoming familiar with the Disneyland app prior to your stay. We also still recommend making some time to talk to hotel cast members: they are very knowledgeable and helpful, and they can assist you in making reservations for hotel activities.