Welcome, you will like this site a lot.
here is a link to FBT. If you go up to "articles" you find a lot of stuff to help you.
http://www.cakecentral.com/article12-How-To-Create-a-Frozen-Buttercream-Transfer.html
All the acronym's used at cake central are in the following post
http://www.cakecentral.com/cake-decorating-ftopict-2926-acronyms.html
As far as a cake extender, it is a recipe of ingredients that you add to a cake mix to change the flavor and add batter to a single box mix, in case you are doing a larger pan and don't want to use 2 boxes, or if you want a chocolate coffee flavour ect. Welcome, you will learn a LOT here. I have. 
a cake extender is exactly what it is like it sounds....by adding a few extra things...you can actually make a more batter from your regular old cake mix...check out the reciepe section or the forums to get some great cake extender reciepes!!! don't worry I'm only up to Junior status on here and I still get confused on the shorthands...welcome...you'll get addicted..trust me...my husband doesn't even ask anymore what site I'm on the internet looking at...he just assumes.. ha ha
Welcome to CC, this is the cake mix extender that I use, it is just wonderful and I use it all the time. Just mix box mix as directed on box and then add the rest of the ingredients below, hope this helps
1 egg
1 cup flour
1 cup sour cream
1 cup white sugar
1/3 tsp. salt
1 tsp. vanilla or other suited flavouring
Welcome to CC! I listed as a newbie but I come to this site at least 2-3 times a day to read forums, look at the gallaries, but since I don't post too much each keeps me at newbie status. I wish they would change that and count how many time you visit the site. I love CC!!
-Michele
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