URDF
URDF (Unified Robot Description Format) is a file format for specifying the geometry and organization of robots in ROS. Is an XML format for representing a robot model.
ROS Packages and Interfaces
robot_state_publisher - publishes the state of a robot to the tf2 library. GitHub
sensor_msgs/JointState - a message that holds data to describe the state of a set of torque controlled joints
Example of a launch file that starts robot_state_publisher and joint_state_publisher