Encryption adds security to data by converting it into an encrypted version that is not decipherable by humans. The encrypted texts can be converted back to human-readable format by using the encryption key. This means that only the receiver or sender of the message can read the original contents.  As an example, WhatsApp heavily promotes end-to-end encryption of its user chats. This means the messages sent by you can only be read by the intended recipient and no one else. In a blockchain, encryption is used to add more to the overall security and authenticity of blocks and keeps them secure.