MQTT - How can I control devices on openHAB via Home Assistant?

That makes sense BUT when I look at my configuration (see below) I get confused.

ON Home Assistant


  light:
    - unique_id: my_dimmer
      name: "My Dimmer"
      state_topic: "oh3/dimmer/my_dimmer/state"
      command_topic: "oh3/dimmer/my_dimmer/cmd"
      brightness_state_topic: "oh3/dimmer/my_dimmer/state_bright"
      brightness_command_topic: "oh3/dimmer/my_dimmer/cmd_bright"
      brightness_scale: 100
      payload_on: "ON"
      payload_off: "OFF"
      on_command_type: last
      qos: 1
      retain: true
      optimistic: false

ON openHAB

channels:
  - id: my_dimmer
    channelTypeUID: mqtt:dimmer
    label: My Dimmer
    description: ""
    configuration:
      retained: true
      postCommand: true
      min: 0
      qos: 1
      max: 100
      commandTopic: oh3/dimmer/my_dimmer/cmd
      stateTopic: oh3/dimmer/my_dimmer/state
  - id: my_dimmer_level
    channelTypeUID: mqtt:colorHSB
    label: My Dimmer Level
    description: ""
    configuration:
      commandTopic: oh3/dimmer/my_dimmer/cmd_bright
      retained: true
      postCommand: true
      qos: 1
      stateTopic: oh3/dimmer/my_dimmer/state_bright