Long story short, Unity will make it easier for you to develop a multiplayer game.
Unity has announced UNET, a set of multiplayer tools and technologies for the Unity Engine, that will make it easier to create multiplayer games using Unity. The UNET suite’s stated goal is to ‘democratize multiplayer game development,’ and the Unity team, a lot of whom worked on MMORPGs before they joined Unity, are all bringing their considerable experience with them to achieve that goal.
Unity will try to implement UNET the same way it always introduces new technologies- in phases, with feedback gathered in each phase being implemented into the next one, and each subsequent phase more complex and full featured than the last. Phase 1 will be introducing a series features to the engine. These include:
High performance transport layer based on UDP to support all game types
Low Level API (LLAPI) provides complete control through a socket like interface
High Level API (HLAPI) provides simple and secure client/server network model
Matchmaker Service provides basic functionality for creating rooms and helping players find others to play with
Relay Server solves connectivity problems for players trying to connect to each other behind firewalls
The actual process that Unity is using to implement UNET sounds very complicated and technical- if you feel up to it, make sure to check it out on their website.