It is possible to move a clip vertically, or from track to track, while constraining its movement horizontally, or in time. In other words, you can move the clip to another track, but maintain its position in time. This can come in very handy.
To do this, click on the clip with the Select tool to select it, then hold down the Control key when you drag the clip to a new track. This works the same on Mac or Windows keyboards.