For the fees, every time a transaction is made with the pair (i.e. swap.Hive and Leo), a small percentage of that transaction is added into your pool. For instance, and using hypothetical numbers here, 6 Leo is exchange for 1 swap.Hive, and you own 1% of that pool --> you earn a tiny bit of Leo (maybe 0.00001) and swap.Hive (maybe 0.00000001) and that amount is "deposited" into the pool as if you invested additional swap.Hive and Leo.