This guide provides an overview of deployment diagrams and how they can be used to understand the structure of a system. It explains the components of a deployment diagram, how to create one, and how to interpret it. It also provides examples of deployment diagrams and tips for creating
From Wikipedia
A deployment diagram "specifies constructs that can be used to define the execution architecture of systems and the assignment of software artifacts to system elements." To describe a web site, for example, a deployment diagram would show what hardware components ("nodes") exist, what software components ("artifacts") run on each node, and how the different pieces are connected.