The Align Clips option moves all selected clips to begin at the same time as the clip with the latest start time on the Timeline. Suppose you have selected three clips: one beginning at ten seconds on the Timeline, the second beginning at seven seconds and the third starting at fifteen seconds on the Timeline scale. When you align them, the first and second clip will be moved to the same time scale as the clip that starts latest i.e. the third one starting at fifteen seconds on the Timeline. Now all three clips will start at fifteen seconds.
The Align Clip also moves non-selected clips that follow the selected clip in the same track. In this case, the Align Clip option moves the non-selected clips by the same amount that it moves the selected clip.
To align clips on the Timeline: