Blockchain is a digital ledger that records transactions in a secure and decentralized manner. Originally, it was used to power Bitcoin, the first decentralized digital currency, but since then it has been adapted for a wide range of applications in various industries.

Blockchain was invented by an anonymous person or group known as Satoshi Nakamoto in 2008. Its main idea was to create a distributed database that would eliminate the need for intermediaries such as banks and other financial institutions.

Here are the top 5 blockchain sites:

1. Bitcoin.org – This is the official website of Bitcoin, the first and most well-known cryptocurrency. It provides information on how to get started with Bitcoin and the latest news in the industry.

2. Coindesk.com – This is a leading media outlet covering news and analysis on cryptocurrencies and blockchain technology. It also features a real-time price index for cryptocurrencies.

3. Ethereum.org – Ethereum is the second-largest cryptocurrency after Bitcoin. Its official website provides information on how to use the Ethereum blockchain, as well as news and updates on the latest developments in the industry.

4. Blockchain.info – This is a popular website that provides a free bitcoin wallet service and real-time data on the Bitcoin network, including transactions, blocks, and nodes.

5. Cryptovest.com – This is another media outlet covering cryptocurrencies and blockchain technology. It features news, analysis, and research on the latest trends in the industry, and also provides a comprehensive list of ICOs (Initial Coin Offerings).