You're reading the documentation for a version of ROS 2 that has reached its EOL (end-of-life), and is no longer officially supported. If you want up-to-date information, please have a look at Iron.
This is a collection of controllers that work using the “position” joint command interface but may accept different joint-level commands at the controller level, e.g. controlling the position on a certain joint to achieve a set velocity.
Hardware interface type
These controllers work with joints using the “position” command interface.