Hi ... you. Actually I don't know if I should call you gudim or gudi.
The rich: tags and a4j: tags are quite a bit different. The rich: tags provide GUI widgets like a calendar, menues, a pick list, suggestion boxes, modal dialogs, etc. The a4j: tags are involved with capturing events, creating AJAX requests, and rendering AJAX responses. There's really not much overlap between the two tag sets.
For links, I have the JBoss RichFaces Developer's Reference bookmarked, and I refer to it often. I also have the book "Practical RichFaces" by Max Katz, but I don't find that as useful as the online documentation. You can also Google for the Exadel RichFaces Demo pages, which show you some of the tags in action. I believe you have to register for the site, but it's free.
a4j and RichFaces started out as separate products. These days they are distributed as a unit. RichFaces functionality is built on the a4j infrastructure.
"a4j" stands for "AJAX for Java". Tags belonging to this namespace handle mostly low-level AJAX support. That is, they tend to be more functional than graphic. RichFaces is primarily about the UI. Aside from that, the only other difference is that the a4j tag chapters precede the rich tag chapeters in the RichFaces user's manual.
An IDE is no substitute for an Intelligent Developer.