The move_base node is from a package called move_base. The main function of this package is to move a robot from its current position to a goal position with the help of other navigation nodes. The move_base node inside this package links the global-planner and the local-planner for the path planning, connecting to the rotate-recovery package if the robot is stuck in some obstacle and connecting global costmap and local costmap for getting the map.
The move_base node is basically an implementation of SimpleActionServer, which takes a goal pose with message type (geometry_msgs/PoseStamped). We can send a goal position to this node using a SimpleActionClient node.
The move_base node subscribes the goal from ...