Here’s a good post on an Introduction to the different Architecture Diagrams in Visual Studio 2010.
To sum up..
- Use Case
- Layer Diagrams
They should be use in this order, except for the Layer one. Which can be done whenever I believe. There’s another one, Dependency Graphs, see original post, page 2 for more info.
…a summary of who is using the application, and how they plan on using it…
…is used to show a software process or business activity as a workflow through a series of actions…
…used to show interactions between different objects in the software system…
…laying out the different components in your system, and how they interact…
…used to describe the different objects in the application being developed…
…allow you to describe the "logical" architecture of your application…