There’s actually two (at least) conceptual models in networking: the OSI model and the TCP/IP model. I had assumed they were the same – vaguely – but they are related in the best way that layered ideas could be: TCP/IP can be mapped onto OSI if you consider OSI as a generic model of a “communications stack.”
If you hear the phrase “Ethernet is layer 1 and 2 of the OSI model” or “TCP is the layer 4 protocol of the OSI model,” that means the TCP/IP concepts are fitted in the OSI stack from Physical (layer 1), Data Link (layer 2) to Transport (layer 4), and beyond.
Regarding network tools, it seems there’s a lot of emphasis on packets: filtering packets, inspecting packets, crafting packets. Less so, seemingly, on the wrapped portions of the data, into frames and segments, and the transmission of bits.
Perhaps because the “transport” layer in both models are the boundary between the application space and the data flow, where the best vectors can be found.