OSI Model Explained — interactive deep dive

The OSI model is easiest to understand as a stack of responsibilities rather than seven definitions to memorize. A browser creates application data, higher layers prepare its representation and conversation, Transport gives the conversation end-to-end delivery semantics, Network chooses an inter-network path, Data Link delivers across one local link, and Physical turns bits into signals. The same message therefore changes form as it moves down the sender and back up the receiver.