Explain how the transport layer correlates with process-to-process delivery?

The transport layer is in charge for process-to-process delivery of the intact message. An application program running on a host machine runs a process but the network layer run source-to-destination delivery of individual packets and it does not have any relationship between those packets. It's treated independently, as though each packet belonged to a separate message. The transport layer task is to ensure that the entire message arrives without error and in sequence and handles error control and flow control at the source-to-destination level.