Stake for Charity (S4C) is the possibility for a HYP holder to devote a part of his stake to a cause of his choice (be it your child, the Red Cross, or the bounty wallet). It is disabled by default and the value of staking can be any integer between 1 to 50%.
This only applies to stake. Thus, you are not losing anything, you are gaining a bit less (well, one can say you are losing profits... semantics and half-empty bottle). You are also earning much more good karma.
Stake for Charity first appeared in HoboNickels and was created by Tranz, but was not available within the graphical wallet and was limited to 1%. It then was extended to BottleCaps as the auto saving feature, where it can be used for other reasons, like sending to a cold wallet, the intented purpose for BottleCaps.
HyperStake is the very first crypto to have a graphical and flexible S4C.
Stake for Charity is part of the wider HyperSend feature.