Kneel for science three-terminal voltage regulator knowledge, 7805, LM7805, k7805,c431, tl431, lm431, LDO and so on what is the relationship between these ics?

78xx, LM78xx, k78xx, is a voltage regulator, providing a stable DC voltage for the back end, ensuring the stable operation of the back end circuit, and protecting the back end circuit from being damaged by high voltage.