What is a Mempool in Crypto?
To better understand how a Mempool works, we'll assume you are a Bitcoin or a Litecoin holder.
Let's go back to the first day you received your coin—and I'll assume you bought it somewhere.
If you remember well, your coins arrived after some few minutes. Others had to wait for a few hours--depending on the state of the network.
The wait time, in this case, is directly proportional to the state of Bitcoin/Litecoin ‘Mempool.’
For simplification, we can describe a Mempool as a 'waiting room' for pending transactions. Why? This is because public payment systems rely on a network of special nodes called miners.
Miners confirm transactions haphazardly, determined by transaction fees.
If you are willing to pay $50 as fees to send $20, be assured that transactions will be confirmed immediately—especially so if transaction fees paid are above rate.
Transaction fees fluctuate, especially in Proof-of-work networks like Bitcoin and Ethereum, because the Mempool size also changes. When there is high traffic, the 'holding room' gets crowded. As such, it will take longer for a miner to confirm a transaction.
In this state, a user who pays lower transaction fees will have to wait longer for confirmation.