This is a feature on the Hive blockchain where users are able to curate content based upon the stake they have.
Content that is posted is eligible for votes during a 7 day voting window. During this time, votes are calculated in accordance to the changes in stake throughout the period. Once that period ends, the voting window closes and the post is paid out of the reward pool.
The window also applies to comments made on Hive.
Rewards are distributed as either 100% Hive Power or users can opt for a 50/50 split between HP and HBD. The choice applies to posts. Comments are always 50/50 payouts.