Mempool in the Bitcoin network is a bunch of all transactions awaiting confirmation by miners. When the miner takes a transaction to include it in the next block, it automatically receives the first confirmation.
Professionals are monitoring the workload of the memepool because, at the moments of recession, you can set a minimum commission and hope for a quick confirmation of the transaction. And vice versa: the more memepool is loaded, the higher the transaction fee.
But we like to give new meanings to the terms, that's why memepool is also a pool of memes here — come on in to lift your spirits.