Dende is a namekian child that was saved by dodoria by gohan on the planet namek. Dende is a lot like gohan he is timid shy and not that strong but unlike gohan he doesn't get stronger. Dende has the ability to heal people that he feels is really kind. Like when he refused to heal vegeta when vegeta had krillin blast a hole through him as part of a plan to make him a super saiyan or at least powerful enough to defeat frieza.
Frieza killed Dende knowing about his ability to heal and figured that if he didn't kill dende the z-fighters would just keep on coming back again and again. Dende was later brought back to life with the earth dragonballs then transported to earth with the namekian dragon balls as well as everybody on namek except for frieza and goku, to his wishes.