*sniff* I'm so proud of you, parser, my star pupil. (my only pupil. and not really actually my pupil).

...methinks you may have used that appvar technique from my GPOS thread? (it's totally fine, I'm just curious)

Assuming you're talking about the OS's Pic0-Pic9 and not an Axe pointer name, yes they are the same from a coding perspective.  To the OS, they are a little different though.  When the OS sees a Pic1 it assumes its a picture and will let you use all those BASIC commands on it.  When you use an appvar, the OS will not really let you do much to them and the only place you will see them is in the memory management screen.  Also, appvars will take up more room in RAM since they also have names which are up to 8 characters long.

But yeah, other than that, you can store data to anything and use it just the same: appvars, pics, strings, lists, even the OS vars.  But the best option for regular data is probably the appvar because its invisible to the end user and can't be deleted accidentally unlike a pic or string for instance which will get overridden constantly by BASIC programs.

GPOS stands for Game Programming On Steroids, I'm assuming you didn't then

What do you mean by graph screen?  L6 is indeed the pointer to the main buffer, where the graphscreen images are stored. 

If the data is already on the graphscreen when the Axe program is run, the data will be stored in L6.