Video has a top and bottom half. The top half shows what you would
see looking at a nearby star over time from Earth. The nearby star,
whose distance you are trying to measure, is in red and can be observed
to move against the fixed background stars. The bottom portion shows
the view of the Earth/Sun/star system from above. The Earth is shown
in blue orbiting the Sun (yellow). The line of sight from the Earth to
the nearby star, and onto the distant background stars, is shown in
red. As the Earth orbits the Sun, the line of sight to the nearby star
changes, and the apparent position of the star on the sky (in the top
portion of the diagram) can be seen to change as well.
In the movie two different cases are shown, one after another. In the
first, the nearby star is closer to the Earth, while in the latter, it
is further away. The size of the apparent shift is shown to be smaller
when the star is further away.