The MonoBridge establishes a connection between your scene and the coherence Replication Server. It makes sure all networked entities stay in sync.
When you place a GameObject in your scene, the MonoBridge detects it and makes sure all the synchronization can be done via the CoherenceSync component.
At runtime, you can inspect which Entites the MonoBridge is currently tracking.
A MonoBridge is associated with the scene it's instantiated on, and keeps track of Entities that are part of that scene. This also allows for multiple connections at the same time coming from the game or within the Unity Editor.
When using a Global MonoBridge (Singleton), the MonoBridge is still associated to the scene it was originally instantiated on, even when the GameObject deattaches from the scene and becomes part of DontDestroyOnLoad.

Persistent Entity limits

Currently, the maximum number of persistent Entities supported by the Replication Server is 32 000. This limit will be increased in the near future.