While it is indeed really simple, understanding of these concepts are important in dealing with XSRF and CORS concepts with in modern browser. I will refer this blog spot in explaining advanced concepts.
The Artifact is generated through Enterprise Architect and YES, i have a valid license to use it. It is drawn as per UML spec. You can download these diagrams, if you like them.
The below shows servlet initialization.
The below shows what happens when user types a url in the browser.
