Raffles are, well raffles and they can be made both public or private.
In a public raffle, anyone can join, but in a private, you need to get an invite from the creator.
And later, when the raffle "happens" a random person is selected for each prize in the raffle.
The winners get a notification, and will then have to contact the creator of the raffle to claim their prize.
So, basically, this is just a random number generator for raffles, with fancy graphics.