Snip!t from collection of Alan Dix

<p>Fundamentally, our system is designed to be run across two components: the web front end and the back-end (commonly known as the "application server" in SharePoint parlance).</p> <p><img style="border: 0px none; display: inline;" title="FeandAppServerDiagram" alt="FeandAppServerDiagram" src="http://blogs.msdn.com/blogfiles/officewebapps/WindowsLiveWriter/DeployingOfficeWebAppsintheEnterprise_98A2/FeandAppServerDiagram_3.png" mce_src="http://blogs.msdn.com/blogfiles/officewebapps/WindowsLiveWriter/DeployingOfficeWebAppsintheEnterprise_98A2/FeandAppServerDiagram_3.png" width="500" border="0" height="225">&nbsp;&nbsp; </p> <p>As illustrated by the above diagram, the front-end components consist of a series of web pages and handlers that are largely responsible for generating and returning an HTML based representation of the document to the browser.&nbsp; Additionally, some, but not all, of the front-end components rely on assistance from the backend in generating this representation of the document. These backend components, which consist of a series of services ("shared applications," again, in SharePoint parlance), are responsible for heavier weight operations, such as performing calc in the case of Excel, or generating an image based representation of the document or presentation in the case of Word or PowerPoint.&nbsp; The front-end components leverage the output of each of these backend services in order to produce the final view of the document in the browser.&nbsp; </p>