ELI5: blockchain

// eli5

What is blockchain?

Blockchain is like a notebook that lots of people share and watch together [2]. When someone writes something in the notebook, everyone gets a copy, and once it's written down, nobody can erase it or change it [5]. It's like a chain of boxes, where each box holds information and is linked to the box before it [2].

Why does it work?

Instead of one person keeping the notebook (like a bank keeping your money records), lots of computers around the world each keep a copy [5]. If someone tries to cheat and change their copy, everyone else's copies don't match, so everyone knows something fishy happened [2].

What can you use it for?

Blockchain helps people trade things like money or digital stuff without needing a bank or company in the middle [4]. You can also use it to keep track of who owns what, like a scoreboard that nobody can mess with [4].

Is it safe?

Yes, because every record is locked together with special math codes (called cryptographic hashes), so changing one thing would break the whole chain and everyone would notice [2].