An official FAQ for Minecraft Dungeons has been released, and it contains a couple of interesting details. First up, we learn that the game can only be played with friends across all platforms. You can play locally with friends, or you can hop online and play with people on your friends list. If you're looking for online play with random people, that's not going to be an option.
As far as online play goes, that's going to be a platform-specific playerbase at launch. Minecraft Dungeons will only let you join up with friends on the same platform when it first releases, but the dev team is looking to include cross-platform play in a free patch after launch. No specifics were given on the release date for that update.
The FAQ has a ton of other important details on the game, as well as a rundown of what to expect. Check out the full FAQ here.