Today’s Ethereum (ETH) was formed through a hard fork off the original blockchain. That original blockchain then came to be known as Ethereum classic (ETC). So why did the fork happen in the first place? The problem arose after one of the most successful ICOs on the Ethereum network. The idea was to create a way for people to contribute to projects from all over the world using ether tokens. Then the participants would share in the profits from the project according to their investment. This project was called the Decentralized Autonomous Organization (DAO).
By the end of the ICO period, about $150 million had been raised from all over the world. Afterwards, some hackers found a vulnerability that simply enabled them to allocate a third of the funds to themselves, fooling the system that it was for a project. This was a huge loss that send shockwaves to the crypto industry, as investors panicked and dumped their DAO tokens. That is where the disagreement started among Ethereum developers.