All cryptocurrencies and crypto wallets reside on a blockchain. There are many blockchains around the world and they share many of the same characteristics.
The first is that they are a decentralised public ledger. In other words they are not owned by one entity but exist on many different servers around the world known as nodes. There are approximately 47,000 bitcoin nodes.
Secondly, blockchains are laid down in, wait for it… blocks. The blocks are verified by the nodes and then committed to the blockchain. Each block is linked to the previous one by a timestamp. The blocks are irreversible.
Which brings us onto the third characteristic of a blockchain: immutability. Blocks are stacked upon each other and once committed to the chain, they can never be altered. That means there is a permanent record of every transaction.