Remember that the OSI model is just a model, and nothing in the real world actually adheres to it.
I believe what this is trying to get across to you is that the application in one host is peering with the application in the other host. Also, the transport protocol in one host is peering with the transport protocol in the other host, the network protocol in one host is peering with the network protocol in the other host, and the data-link protocol in one host is peering with the data-link protocol in the other host*.
The data that one application sends to the other application ends up in the destination application unchanged. Yes, as the data moves down the network stack in the sending host, it gets headers from the various network layers attached to it, but as it travels up the network stack in the destination host, those headers are stripped off, leaving the original data from the source unchanged.
Each network layer in the source host adds a header for the corresponding network layer in the destination host, and the corresponding network layer in the destination host will strip off the header, leaving the PDU for the next layer unchanged form the source.
*This hold true for the data-link layer only if both hosts are are the same data-link LAN. If the network packet must cross to another LAN, each router in the path will strip off the data-link header, replacing it with its own
data-link header for the next network through which it will forward the network packet.