When either Touch, Latch, or Write mode is active, you can record automation in record or playback mode. Whatever you touch or move is recorded, based on the chosen mode. When not recording or playing, the modes are ignored, and no data is written if a control is moved.
You have the following Write options for track automation:
Move any fader or control on the selected channel strip with the automation mode set to Touch, Latch, or Write. In real-world usage, you’ll rarely (if ever) use the destructive Write mode, which erases all automation. The standard Write modes are Touch and Latch.
Choose a parameter from the Automation Parameter pop-up menu in the track header, then adjust the numerical display in the track header, with one of the modes turned on.
Move the faders or knobs of a connected hardware controller, with one of the modes turned on.
Use the Pointer or Pencil tool to draw your automation curve.
You can specify the mode that the application switches to after a Write operation has been performed using the Automation Preferences pane.