What does dedication mean? For example, there are tend people and only one of them has food. The owner of the food could just keep it for self consumption. Instead, out of compassion, the food is shared with the other nine. Dedication is similar to this sharing. The good seeds sown by virtuous actions that people perform will bear virtuous fruit. Mahayana practitioners, unwilling to enjoy the positive karmic result by themselves alone, give the fruit to all sentient beings to share. This is what dedication connotes. 

~Depicted from From Believers to Boddhisattvas