TL: DR; The Ethereum mempool is a waiting area for unconfirmed transactions. When a transaction is sent on the Ethereum network, it is broadcast to other nodes and must go through a series of validity checks before it can be added to a block and confirmed. While it is waiting to be confirmed, it resides in the mempool. The mempool is also known as the "pending transactions" or "txpool." Each node has its own mempool with its own rules for accepting and dropping transactions, which are determi...