How does a blockchain ledger verify transactions securely?

A blockchain ledger is like a group of friends who all agree on what happened at recess so no one can cheat.

Imagine you and your friends are playing a game where everyone puts coins in a jar when they do something fair, like sharing toys. But if someone takes extra coins without doing their part, the whole game gets unfair. So to make sure everything is fair, every time someone adds or takes coins from the jar, all the other kids check it.

Blockchain works like that big jar, but instead of coins, it holds transactions, and instead of friends, it has computers called nodes. Each time a transaction happens, like when you send money to your friend online, the nodes check if it's real and fair.

Every time someone adds a new transaction, all the other nodes get a copy of it. They compare it with their own records. If they all agree, the transaction is added to the ledger, like adding a new note in the jar’s history.

If someone tries to cheat and say they sent more money than they had, the others will notice because their copies don’t match. That's how blockchain stays secure, everyone has to agree on what happened!