A MEMPOOL (short for memory pool) is a component of a cryptocurrency node or wallet that stores unconfirmed transactions that have been broadcasted to the network but have not yet been included in a block.
When a user initiates a transaction on a cryptocurrency network, the transaction is broadcasted to nodes in the network. These nodes verify the transaction and propagate it to other nodes. If a node determines that the transaction is valid and meets the network’s rules, it adds it to its mempool.
Miners, who are responsible for adding transactions to the blockchain, select transactions from the MEMPOOL to include in the next block they mine. Transactions with higher fees attached to them are usually prioritized by miners, as they have a financial incentive to do so.
If a transaction remains unconfirmed in the MEMPOOL for an extended period of time, it may eventually be dropped from the mempool if it is not picked up by a miner. When this happens, the user may need to initiate the transaction again with a higher fee to ensure it is included in the blockchain.