With Track Automation you can automate parameters over time in a track. Currently only track volume and pan. Click the automation button on a Track Panel and select the parameter you want to automate to activate the automation view.
After activating a parameter for automation, you will see a grey line appear over the track in the arrangement. This is the currently inactive automation line. Click the grey line or double-click above or below it to add new automation points. Add several points and click and drag these around to create your desired automation curve. Select several automation points by clicking them while holding down your Alt key. You can also click, hold and drag a selection box from above or below the automation line.