"We are also capable of directing attention toward or away from encountered stimuli based on our goals (top-down modulation)"

In Top-Down visual perception one sees what one is looking for based on accomplishing an internally driven goal. It is a bias form of perception, sort of like the saying "selective hearing". For example in this picture of...

Now depending on what your looking for, your definition of what the picture is about will be different. I like jets so to me it's about jets. For those who are into land formations or farms perhaps the picture is about the fields in the background. As I focus on the jets the fields fade whereas for the field lovers the jets fade. Definitions of what one sees vary even when looking on the same thing because we see what we want to see depending on what we want to accomplish regardless of how correct the interpretation, and that my friends is what I believe to be top-down visual perception's vibe.

Photo from: http://upload.wikimedia.org/wikipedia/commons/9/97/F-16_and_F-16XL_aerial_top_down_view.jpg

Quote from: http://gazzaleylab.ucsf.edu/topdown-background.html