std_msgs contains common message types representing primitive data types and
other basic message constructs, such as multiarrays. For common, generic
robot-specific message types, please see common_msgs.

std_msgs contains wrappers for ROS primitive types, which are documented in the
msg specification. It also contains the Empty type, which is useful for sending
an empty signal.

This package also contains the "MultiArray" types, which can be useful for
storing sensor data.