Beaglebone Green (Short as BBG) is a joint effort by Beaglebone.org and Seeed Studio and it was derived from Beaglebone Black (Short as BBB). If you ever heard of BBB, you may know that BBB was the most popular board in the Beaglebone board family. It is much cheaper than previous version while inherits all the good features of Beaglebone. BBG is better than BBB, Seeed Studio has kept almost all the good features of BBB such as the tiny size, abundant interface and strong expansibility, while at the same changed it a bit to make it more powerful.
The main change is replacing the HDMI interface with 2 grove connectors. Grove is a great invention by Seeed, it is a modular standardized connector prototyping system by which you are able to build applications without soldering and jumperwires. With the rapid development of the grove system, more and more sensors, actuators, displays are joining in the grove family, all of them are integrated the standard grove connector, so that you can connect the BBG to them with a simple cable. So far Seeed has produced more than 30 groves that work well with BBG, and the number is increasing. Apart from that, they also changed the 5V barrel to be micro USB host, so that you can power the board more conveniently.
Despite of the changes that were made, BBG is still fully compatible with BBB and applied with all the BBB capes. Even though BBG has all these advantages, the price did not increase, actually the price of BBG is much lower, it may be the most low-cost BeagleBone in history. What Seeed want, is to provide a BeagleBone that is not only more powerful and easy-to-use, but also reachable to most people.