The solutions your miner sends are "shares", or proof that you're doing some work.
If (simplified) you need to hit 0x0000CCCC to win the block, and you send in 0x000FFFFF the pool has a pretty good idea that you are working to solve the block. I don't know what exact measure counts as a share though, it must be some minimum amount compared to the target value.
There isn't a new block every second because the target value adjusts over time to account for how much hashing power is in the network based on how quickly blocks were found over the last 2016 blocks. If the target is 0x0000CCCC, that is what it takes for 10THash/s to find a block every 10 minutes, on average.