Hey Lassie,
You seem like a new Amiga user. I only say that because you've posted a lot of questions lately with some fairly legitimate fundamental questions.
There's an awful lot of great resources out there already that may already have the exact answers you are seeking. For instance, the Big Book of Amiga Hardware, AmigaWiki, etc.
Google can help you find many of these answers:
http://lmgtfy.com/?q=amiga+rtg+graphics+card
Also, the "search" function here at Amiga.org can return a treasure trove of past threads on many of these fundamental topics. I'm sure we've discussed a lot of these probably a half a dozen times or more over the years.
Good luck with your Amiga exploration! Have fun!
