Tami, who knows what it is, but it benefits all the crew, rather than just your steward/stewardess in your cabin. They use this for many things I have heard about, bikes on board for them to use? Air tickets home for emergencies, all sorts of stuff, and it benefits the workers, not the officers to my knowlege. All good. But YOUR choice. Just do what makes you feel good, but cash tips are certainly not "expected".