Blockchain is a continuously growing list of records (blocks), which are linked (chained) using cryptography.

• Transactions are timestamped and hashed into an ongoing chain.
• These hashed transaction records are called blocks.
• You can't change blocks without redoing the proof-of-work.
• Blockchain is secure as long as honest nodes collectively control more CPU power than any cooperating group of attacker nodes.

Data on a blockchain is unencrypted. It has to be by design as nodes need to validate it.

Not all information on a blockchain is correct. The data still needs to be checked for malicious intent or human error.

It is challenging to remove data. Sometimes laws require you to exclude specific data.

It is not inherently secure. It depends on the assumption that the community has more compute power than a potential attacker.

Sources

• APNIC - Don’t get caught up in blockchain hype
• Wikipedia - Blockchain