A protocol stack in networking refers to a set of protocols that work together to enable communication over networks. Comprised of several layers, each with specific functionalities, the protocol stack ensures that data is transmitted reliably and efficiently across various networks. The most common model is the OSI (Open Systems Interconnection) model, which consists of seven layers. Each layer serves distinct roles, including managing data transmission, addressing, and error handling. Understanding protocol stacks is essential for network design and troubleshooting.