What is the "LEGO Master Builder Academy"?
Basically, it's a program in which LEGO Master Builders share and impart their LEGO building knowledge to members. If you remember LEGO BrickMaster, MBA is sort of a successor to that.

There's a Guide section in the LEGO MBA site that answers your questions. Specifically, from What is LEGO MBA?:

What is this "Academy"?


  LEGO Master Builder Academy is an in-home and online experience in which real LEGO Master Builders share the tips and techniques of basic through advanced building, creativity and design with kids (ages 8 or older) who want to become better builders.


What do I get with the set?


  The first annual subscription includes LEGO MBA kits 2-6, with one kit delivered every 2 months, plus unlimited access to the members-only LEGOmba.com website! Each LEGO MBA kit includes an 84-page Designer Handbook teaching LEGO Master Builder techniques, plus articles, building instructions full of Master Builder tips, LEGO bricks to create 3 new models (one at a time), and exclusive minifigures or accessories.


How much does it cost?


  The subscription, which includes kits 2-6, is $69.99 and available for purchase online or by phone.


This "about" page and the rest of the site should answer some other questions you might have.