Most of the time, Charity Engine will be working for ethical companies who have hired the grid, with the profits going to charity and the prize draw.
Sometimes the work will be scientific or medical research (our favourite), sometimes it will be boring commercial tasks. But whatever work it is doing, the result is exactly the same: your PC will be raising money for the world's best charities.
If Charity Engine has surplus capacity (eg. no paying work for your PC right now), then it will default to helping one or more existing humanitarian BOINC projects - and yes, that will still earn you prize draw entries.
Charity Engine does good work, all the time. We don't waste a bit...!