Simplify the following text for a Grade 9 native English-speaking person.
Original: A semi-postal stamp or semipostal stamp is a philatelic term for a postage stamp issued to raising funds for some purpose , usually for a charitable cause , such as the Red Cross .
Simplified: A semi-postal stamp or semipostal stamp is a postage stamp issued to raise money for some purpose ( such as a charitable cause ) and thus sold over and above the cost of postage .