visualization_msgs is a set of messages used by higher level packages, such as rviz, that deal in visualization-specific data.
The main messages in visualization_msgs is visualization_msgs/Marker. The marker message is used to send visualization "markers" such as boxes, spheres, arrows, lines, etc. to a visualization environment such as rviz. See the rviz tutorial rviz tutorials for more information.
visualization_msgs is a package to collect all visualization-related messages into one place.
The messages it currently contains are: