Hi, Karyn,
FAA uses the terms 'posters' and 'prints' interchangeably. Here's a recent discussion:
http://fineartamerica.com/showmessages.php?messageid=2001987
I think it's an unfortunate and confusing misnomer, as most buyers don't consider 'posters' and 'prints' to be the same thing. Unnecessarily confusing, imo.
As for Acrylic Prints -- go to any of your prints, click on the Acrylic Prints option, and scroll down that page to see a full description of acrylic prints. The sheet of acrylic is 1/4" thick; not nearly as thick as canvas. But not as flat as paper, either.
Have that extra coffee -- try stirring in a spoonful of chocolate syrup. That's a kickstarter, for sure! :-)
EDIT, @Kevin -- Papers used here are archival and beautiful. Seeing the high quality of FAA prints is what convinced me to become a member.