Gazebo is a multi-robot simulator in a 3-dimensional world. It comes with advanced plugin interfaces that can be used to simulate the sensor feedback and plausible interactions between objects. Robots and other objects can be modeled into gazebo using their SDF. Apart from these, there are standard models available within gazebo that can be used with custom models. To learn more about gazebo visit the gazebo wiki.
Baxter with Gazebo
Baxter is modeled into gazebo using its URDF. Controller plugins like block laser, point laser, and cameras are used to simulate the sonar, IR and the cameras on Baxter. The simulator can be used in conjunction with the rviz and moveit as with the real robot.
Do I need to learn Gazebo to work with the Baxter simulator?
No, you do not need to learn Gazebo. Basic ROS knowledge should suffice to get you started.
Does this version work with ROS-Hydro?
Currently, Baxter simulator is officially supported only in ROS-Indigo, but you are welcome try Hydro and report your results to the community :)
Is this simulator built using the same SDK software running on the real Baxter?
No, the SDK interfaces were only simulated.
I am an advanced user of Gazebo, how can I contribute to the Baxter community
We would love to see the controllers and other features that you have developed for Baxter.