i know the rules and will try to explain:

there are rain pool, witch is filled by satoshis. for example, send msg in chat, cost 10 satoshies and 50 % of this 10 satoshi goes to rain pool, also any player can tip and fill this rain pool with any amount of satoshies, and on every hour, this rain pool will be divided equally to 50 lucky players, who had made even one msg on previous hour.

hope i have explained clearly.