Bricktronics Library Interface (API)
Here is an unfinished page outlining the API for the new Bricktronics v1.2 libraries. An API describes the different ways to interact with the libraries.
Bricktronics Shield and Megashield
The BricktronicsShield and BricktronicsMegashield libraries are used primarily for initializing the other libraries for the motors and sensors, because these libraries contain the list of which motor/sensor pins are connected to which Arduino pins for both the Bricktronics Shield and Megashield. Additionally, the Bricktronics Shield library also contains helper code to work with the I/O expander chip on the Bricktronics Shield.