When your device gets stuck in a bootloop, it's your device's way of trying to "turn it off and on again" to fix the issue. But, of course, because there's an issue in the booting process, it keeps running into that error over and over again. But what actually causes a bootloop...
Hard brick is the state of android device that occurs when your device is unbootable without a bootloop. A hard Brick device generally show little to no signs of life. If this happens, you had better to buy a new device since your device is showing you a black or grey screen at this ...