Lollipop 5.0 introduced sliding heads-up notifications instead of the scrolling status bar ticker that had been used on all Android versions prior. They showed up on top of your current screen for a few seconds, then went back into the notification tray. However, the function still seemed quite unfinished, with notifications blocking everything underneath them unless you completely got rid of them or waited for them to disappear. Lollipop 5.1 made it possible to dismiss notifications with a swipe up, sending them back to the tray so you can check them later.