ELI5: what is blockchain

What is blockchain?

Blockchain is like a notebook that many people share together, where everyone writes down the same information [1]. Instead of one person keeping the notebook, lots of computers all have a copy, so nobody can cheat or erase what was written [4]. It's similar to a classroom where everyone keeps identical notes so nobody can secretly change their answers [5].

Why does it work this way?

Blockchain connects information in blocks that are linked together like a chain [4]. Each new block of information gets locked to the one before it, making it almost impossible to change old information without everyone noticing [1]. It's like gluing pages together—if you try to change page 3, the glue breaks and everyone can see something was tampered with [3].

What can you use it for?

Blockchain keeps track of transactions and who owns what in a way that everyone can trust [1][2]. It's super useful for money transfers, keeping records safe, or proving who owns something without needing a bank or company in the middle [3].

How do computers keep it safe?

Every computer in the network has the exact same copy of all the information [5]. When someone tries to add new information, all the computers check it and agree it's real before adding it [2]. If someone tries to cheat by changing their copy, all the other computers will catch them because their version doesn't match [4].