Transaction

A transaction is a signed instruction that transfers cryptocurrency or interacts with a blockchain — the basic unit of activity every blockchain records. A typical transaction specifies a sender, a recipient, an amount, and a fee, and carries a cryptographic signature created with the sender's private key, proving the owner authorized it without revealing the key itself.

A transaction's life cycle has several steps. It is created and signed in a wallet, broadcast to the network, and held in a waiting area called the mempool until a miner or validator includes it in a block. Once in a block, it is confirmed, and each subsequent block adds another confirmation making reversal ever less likely. For example, sending 0.5 ETH to a friend means your wallet builds the transaction, you approve it, the network includes it in a block — usually within seconds to minutes — and the transfer becomes a permanent public record anyone can view on a block explorer.

A common misconception is that blockchain transactions can be canceled or charged back like card payments; once confirmed, a transaction is irreversible, and no support desk can undo a transfer to the wrong address. On smart-contract platforms like Ethereum, transactions do more than move money — they also deploy contracts and call their functions, so swapping tokens or minting an NFT is also a transaction. Every transaction pays a fee, which compensates the network for processing and secures priority when blocks are full.