Schunk_svh_driver: effort and velocity channel_targets?

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The file quick_commands shows how to set channel_targets:

rostopic pub /svh_controller/channel_targets sensor_msgs/JointState "header:
  seq: 0


stamp: {secs: 0, nsecs: 0}
  frame_id: ''
name: ['Index_Finger_Proximal','Index_Finger_Distal','Middle_Finger_Proximal','Middle_Finger_Distal','Ring_Finger','Pinky','Finger_Spread','Thumb_Flexion']
position: [0.8,1.3,0.8,1.3,0.9,0.9,0.5,0.3]
velocity: [0,0,0,0,0,0,0,0]
effort: [0,0,0,0,0,0,0,0]"

what does it mean with "velocity"? what is "effort"?