A PoS pool would basically be a shared wallet that you send your coins to for staking purposes. If you had 10 F0ME and wanted to stake consistently, you could send them to a pool. When the pool earns a stake, it would divide it up to all the investors at the pool based on the number of coins they have invested. Alternatively, if you left your wallet open with 10 F0ME it might take weeks or longer to stake - so it takes a lot of patience and some luck.