The document discusses the different logical layers in Mule - the model layer, service layer, transport layer, and component layer.
The model layer represents the runtime environment hosting services. A Mule service processes particular requests using a specific configuration defining the elements involved.
The transport layer receives and sends messages using connectors like FileConnector, JDBCConnector and HTTPConnector. Transformers optionally change message formats.
Routers control message flow by routing messages between endpoints. Filters can restrict messages based on conditions. Components execute business logic on events.