The Byzantine Generals' Problem refers to network fraud or errors, using the example of betrayal within a group in the Byzantine Empire, a European empire.

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Long ago, there was a country called the Byzantine Empire.

These nine generals of the Imperial army were leading their troops to besiege another city, A, in order to capture it.
The military strength of the Byzantine Empire and City A is currently evenly matched.
In order to capture it, nine generals were needed.
① All forces cooperate and launch a simultaneous attack.
② Withdraw all troops and rethink the strategy.
There are only these two options.

Of course, this was a time before telephones and email.
Each general entrusted a messenger with the decision of whether to attack or retreat, and communicated this to the other eight units, so that the decision of whether to attack or retreat with all troops could be made by majority vote.

For example, even if you decide to "attack," if you receive a "retreat" order from five or more other generals, you will retreat according to the above instructions.

However, this method may not allow majority voting to function effectively.
That would be the case if there was a traitor among these nine generals.

For example, if four people decide to "attack" and four decide to "retreat",
The traitor sends messages to the four people he believes should attack, telling them to "attack," and to the four people he believes should retreat, telling them to "retreat."
Since the nine generals cannot gather to verify the information, they have no choice but to trust the message they receive.
In this scenario, the four generals who decided to "attack" will attack, and the four generals who decided to "retreat" will retreat. As a result, only four armies will attack, failing to capture city A, and the operation will fail.

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Thus, if even one person in a group spreads false information, it becomes impossible to reach a consensus among the group as a whole.

Using this example as an analogy, the possibility that a small number of participants in a blockchain could betray the system and prevent proper consensus building is known as the Byzantine Generals Problem on a network.

So, how does blockchain solve this problem?

It means rewarding those who act correctly and do not betray others.
This is known as "Proof of Work (PoW)," and it's a system where miners are rewarded for solving difficult computational problems (mining), making it economically more rational for them to take the right actions.