Explain · Like I'm five version
Blockchain in terms of a WhatsApp group chat
A blockchain is just a big WhatsApp group chat where everyone has to agree on what happened before a message can be saved.
In this group chat, you cannot edit or delete any messages once they are sent. Every single person in the group keeps their own copy of the chat history on their phone. If someone tries to change a message from last week, their copy will not match the copies everyone else has. The group will then see that one person is wrong and simply ignore them, keeping the chat safe from mischief.
Adding a new piece of information is like waiting for the group to vote on a new photo. Everyone checks their phones to make sure the new information makes sense and fits with what came before. When most people say it is okay, the new message is locked in forever. It is a bit like a group chat that never goes quiet, even at three in the morning when you are trying to sleep.
Because everyone has the same list of messages, you do not need one single person in charge. There is no group admin who can kick people out or change the rules of the chat. You just need to trust the math that keeps the chat in order, rather than trusting a person. It is a very busy, very honest, and very permanent way to keep a record of who owns what.
Where the analogy breaks downIn a blockchain, you cannot send a funny sticker or a voice note of your cat.