Entitytype is used to keep references to other Entities. Technically the reference is stored as a local index that has to be resolved to an actual Entity before usage. Also, since a Client might not know about the referenced Entity (due to it being outside of its LiveQuery) an Entity reference might be impossible to resolve in some circumstances. Your Client code will have to take this into account and be programmed in a defensive way that handles missing Entities gracefully.
Portalthat has the members
AuthorityOnly- command will be received only by the owner of the target Entity
All- command will be received by every Client that has a copy of this Entity