I am new to SharePoint 2010 and want to learn first how to setup an environment for DEVELOPMENT, STAGING and PRODUCTION. I am actually looking for a diagram which caters all three farms.
I would appreciate if someone can help me for the diagram.
Check out the "Logical Architecture Planning" parts of TechNet - there you got the most of it: http://technet.microsoft.com/en-us/library/ff829836.aspx
Also check the "Design Content Deployment" article at: http://technet.microsoft.com/en-us/library/cc262004.aspx
Rewriting it here is one heck of a job :-)
It's bit hard to answer your question with just a diagram but here we go...
If you are looking how to setup all these servers here is an article on SharePoint 2010 ALM with Team Foundation Server, diagram:
If you are looking how to configure your environment for something like this check the article I wrote for v2007, the diagram:
Without knowing what you need, probably 1 limited deployment for your DEV
And 2x small farms for your stage and prod (remembering you want your stage and prod to be the same)