What is a bipolar capacitor and when is it used?
Bipolar is not commonly used these days (outside of psychiatric circles, of course). The more common term is unpolarized. This is in contrast with polarized capacitors such as electrolytics, where applying the wrong polarity can destroy the cap.

So a bipolar label is typically used to draw attention to a cap whose value is so large that a polarized cap might be expected, but which must not actually be polarized.