The Open Systems Interconnection (OSI) model has layers:
Physical - Electrical signals and cables
Data Link - Node-to-node delivery
Network - End-to-end routing
Transport - Reliable or unreliable delivery
Session - Connection management
Presentation - Data formatting
Application - User-facing protocols
Mnemonic: "Please Do Not Throw Sausage Pizza Away." OSI is a reference model. Real protocols don't always fit neatly, but OSI remains the teaching standard.