Promotional Items are items that cause promotions for units that are at least level 10. In most games (except in Gaiden, Genealogy of the Holy War and the Tellius series) they are required to promote a first tier unit to a second tier unit. They are still present however in the Tellius series in case you wanted a unit to promote early. In the Japanese version of Radiant Dawn they are required to promote a second tier unit to a third tier unit.