Legacy. Hermann Ebbinghausâ lasting contributions to the field of psychology are multiple. In addition to being the first psychologist to study areas of human learning and memory, Ebbinghaus contributed greatly to the establishment of experimental psychology.
This includes dimming the display slightly, stopping Mail push and fetch, turning off background app refresh, turning off Hey Siri, and a few other iOS features. By turning these features off, the battery life of the iPhone is extended dramatically, and when Low Power Mode is enabled the iPhone battery icon is yellow to demonstrate this.
The charging cable icon beneath the red battery icon is another hint that you need to plug your iPhone into a computer or a wall charger. The iPhone still works while it's showing the red battery icon, but it's hard to know how much life it has left (unless you're viewing your battery life as a percentage, that is). It's best to not push your luck. Recharge your phone as soon as you can.