Newbie question: Bitmap vs Graphic

I am newbie to flash and need a good explanation on usage of Bitmap symbol vs Graphic symbol.

I go thru some of the tutorials on this site and saw that sometimes people convert a [color=darkred]bitmap[/color] to a [color=darkred]graphic[/color] symbol then convert the graphic symbol to a [color=darkred]movie[/color], and sometimes they convert a [color=darkred]bitmap directly[/color] to a [color=darkred]movie[/color] symbol. This confuses me.

I tried doing diffenrent things using bitmap and then graphic symbol and notice there is no different.

I bought a book and read thru about this. All they say is if you are not sure then convert everything to a movie, that’s not a good explanation since I want to know for sure and exactly what I am doing.

I read the help from flash IDE, they say to use graphic symbol for static display. What’s wrong with using Bitmap for static display ??? is there an advantage ? and when should you convert a bitmap to a graphic symbol since
you cannot assign an instance name for them, therfore you cannot access them from action script.