Blockchains are the technology that powers Bitcoin, Ethereum, and a rapidly growing number of other platforms and services. Blockchain applications are proliferating, and dominating investment markets today, because of their security and immutability.
A blockchain is a massive, distributed electronic ledger that records transactions in a single, cumulative sequence, each transaction verifiable by anyone who cares to look. This provides an unprecedented level of security for electronic transactions. It eliminates the risk of hacking. (Although hacks often compromise the accounts of individual holders of Bitcoin etc., it is the individual account credentials, and not the core ledger, that are vulnerable to attack. The core ledger is immutable.)
Major financial institutions, and international organizations such as the UN, are adopting blockchains to leverage these benefits. So far, most are focused on financial transactions, but blockchains can also be applied to any purpose where reliability is essential, such as voting.
Blockchain transactions are based on transferring unique digital cryptographic keys. In blockchain voting, each voter has a unique digital key to assign for each vote she chooses to cast, like a ballot. After voting, the voter can see her unique key, along with her voting choice, in the blockchain, to verify that her vote was properly recorded. And everyone can see the entire ledger of votes, collectively monitoring against hacking and ensuring the overall integrity of the system.