Mempool
A mempool is a node’s waiting area for valid but unconfirmed transactions before they are included in a block.
In Bitcoin, the mempool, short for memory pool, is the temporary set of valid transactions that a node has received but that have not yet been confirmed in a block. Each Bitcoin node keeps its own mempool, so there is not one single global mempool, though many nodes will hold a similar set of transactions. When you send a Bitcoin transaction, it is broadcast to the network, checked by nodes, and then waits in mempools until a miner includes it in a block.
The mempool matters because it affects confirmation time and transaction fees. Miners usually choose transactions offering higher fees per unit of block space, so when the mempool is crowded, low-fee transactions may wait longer. A practical comparison is an airport departure board: many valid flights are ready to go, but only some fit into each takeoff slot. Wallets often look at mempool conditions to suggest a fee that is likely to confirm within a chosen timeframe.
Other terms in Bitcoin
ASIC
A specialized computer chip built to do one task very efficiently, commonly used in Bitcoin mining to perform hashing calculations.
BTC
The ticker symbol for bitcoin, the native currency of the Bitcoin network.
Bitcoin
A decentralized digital currency and payment network that lets people send value without relying on a bank or central authority.
Block Height
A block height is the number that shows a block’s position in a blockchain, counted from the first block.