Network protocols are the standardized rules and conventions that govern how data is transmitted between devices on a network. They operate across multiple layers of abstraction—from the physical signals on a wire to the application-layer messages you see in a browser—and each protocol serves a specific purpose in ensuring reliable, efficient, and secure communication. Understanding protocols like TCP/IP, UDP, HTTP, and DNS is essential for diagnosing network issues, optimizing performance, and designing scalable systems. Keep in mind that the protocol stack is hierarchical: higher-layer protocols depend on lower-layer protocols to handle addressing, routing, and physical transmission, so knowing where each protocol lives (and how they encapsulate data) is key to understanding end-to-end network behavior.