You can claim free coins from the faucet every 10 minutes (maximum 10 claims per day).
By "Randomizing", you are generating a new pair of seeds. Before you specify your new client seed, you are shown the SHA256 hash of the server seed that will be used alongside whichever seed you pick. The previous seed pair is revealed and you can check the details by clicking the "CHECK" button next to each bet.
It is revealed after a new pair is generated