[diziet]

Each curve/line is an individual app with each point representing that app's stats in downloads, reviews, etc. You can use the different axis to see trends. Ie, there is (obviously) a correlation between number of downloads and reviews. You can check out a bit about the history of the visualization at http://en.wikipedia.org/wiki/Parallel_coordinates

[oscilloscope]

If the axes were reorderable, you could move Downloads next to Reviews and see the relation without filtering.