The breather hole, or a bleeder hole, as some call it, wears a few hats. To know how it works, firstly, it’s critical to initial know how a window is engineered.
Article source: https://www.huffingtonpost.com/entry/why-there-are-tiny-holes-at-the-bottom-of-windows-on-planes_us_5a904edfe4b0ee6416a2f988