transaction
A Bitcoin transaction is a digitally signed message that transfers value from one or more addresses to one or more addresses. Once broadcast to the network, it waits in the mempool until a miner includes it in a block.
A Bitcoin transaction is a signed instruction that authorises the transfer of value on the Bitcoin network. Every transaction references previous outputs as its inputs and creates new outputs assigned to recipient addresses. The sender proves ownership of the input funds by providing a valid digital signature, generated using the private key associated with the sending address. Without a valid signature, the network will reject the transaction.
Transactions do not move coins in the way physical cash moves. Instead, they consume existing unspent outputs and create new ones. If you receive 0.5 bitcoin and want to send 0.2 to someone, the transaction will consume the entire 0.5 output as an input, send 0.2 to the recipient, and return the remaining amount minus the fee to an address you control. The difference between the total value of inputs and outputs is claimed by the miner as a transaction fee.
Once created, a transaction is broadcast to the peer-to-peer network and enters the mempool, a waiting area where valid but unconfirmed transactions are held. Miners select transactions from the mempool and include them in new blocks. A transaction is considered confirmed once it appears in a block, and becomes increasingly final with each additional block added on top.