Nano (NANO), which was previously known as RaiBlocks, is a digital currency that allows for instant, feeless transactions making it a suitable currency for micro-payments and peer-to-peer transactions.  

Nano accomplishes these feats by using a block-lattice architecture, which just means that each account is assigned its own blockchain and each block is just one transaction.

While most cryptocurrencies depend on either proof-of-work or proof-of-stake to validate transactions, Nano uses what is called Open Representative Voting, where Nano accounts choose a representative account to vote on the validity of transactions.

Each representative’s voting weight is the sum of the NANO balances of all accounts that are delegated to it. Since Nano blocks are very small, the chosen representative is able to validate transactions extremely quickly.

In simplified terms, this just means that each account helps verify transactions for other accounts.