there is a gigantic number of coins that don't even exist in the real world (meaning no announcement, no blockchain, no nothing) they only exist on yobit! some of them have died but some were so shitty that the creators didn't know what to do so they only listed it on yobit.
the way their free coins used to work a couple of years ago was to attract people to their site and increase their traffic. now it works in a way that any user can start a giveaway so they use it to try and sell their shitcoins. for example they place a sell at 1 satoshi (there is no buy orders) then open the giveaway. if you claim it you either have to let it clog your wallet or have to buy the coin to be able to sell it because what you have is smaller than minimum. and when you attempt to buy you would be buying from that person opening the order.
it is a silly thing and i don't think they can make any money from it but they do it anyways.