It’s also worth mentioning that sockets aren’t a real layer, because they’re just an API at the OS level (they’re an abstraction to let application developers use TCP/UDP/etc.). ALSO, in some interpretations, everything above Layer 4 is debatably just the application layer. There’s not necessarily a clean separation between the presentation layer and “application layer” in all applications. That said, the 7 layer model is still useful as a teaching too, but knowing these extra details will give you a more complete understanding (and be less confusing).
It’s also worth mentioning that sockets aren’t a real layer, because they’re just an API at the OS level (they’re an abstraction to let application developers use TCP/UDP/etc.). ALSO, in some interpretations, everything above Layer 4 is debatably just the application layer. There’s not necessarily a clean separation between the presentation layer and “application layer” in all applications. That said, the 7 layer model is still useful as a teaching too, but knowing these extra details will give you a more complete understanding (and be less confusing).