The language is C#.
Each instantiated class exists for the life of the orchestration. It is serialized into the MessageBoxDb at certain persistence points. All the messages, variables and the processing state are saved. If your Biztalk server is switched off, the orchestration will restart from the last persistence point. If your orchestration has a long wait then it is persisted and removed from memory (dehydrated) and can be rehydrated when the event it was waiting for occurs.