Not a silly question at all…Its donating the marrow in your bones IF you EVER Match with a person/child who needs it.Please note that they donot take the marrow out o everyone, its IF you Ever match. I met some people today that have been on the registry for 12 years and never matched.Thats the thing but it sure Definitely Saves a life of Human.You as a donor regenerate the marrow just like blood.
Here is a link.They also do International Registry.
www.marrow.org