I am trying to understand xacros while building my robot model. I am using VLP-16 urdf from velodyne_description package. There is *origin parameter while creating the xacro. What is the purpose of the * ?

I believe then the *origin parameter is used in the xacro:insertblock xacro. Is that correct? Where is the insertblock xacro is defined? What does it do?

VLP-16.urdf.xacro (line 4 and 6):

https://github.com/akhil22/velodyne_simulator/blob/master/velodyne_description/urdf/VLP-16.urdf.xacro

The same usage exist here as well in line 4 and line 16:

https://github.com/ros-controls/ros2_control_demos/blob/master/ros2_control_demo_description/rrbot_description/urdf/rrbot_description.urdf.xacro