An Anchor point is ADAT/Edit's way of letting you determine which part of your file is on the downbeat. Just double click your track to open the Edit Window and drag the black arrow at the bottom of the window (you may have to expand the window a bit) to the part of the wave that you want to "land" on the downbeat. This is handy when your file has a "pick up" and you want to line up a point with the downbeat.