From Blizzard:
Paladins:
Paragons of Justice
This is the call of the paladin: to protect the weak, to bring justice to the unjust, and to vanquish evil from the darkest corners of the world. These holy warriors are equipped with plate armor so they can confront the toughest of foes, and the blessing of the Light allows them to heal wounds
https://worldofwarcraft.com/en-us/game/classes/paladin
Shaman:
A totemic warrior who strikes foes with weapons imbued with elemental power.
http://www.wowhead.com/talent-calc/shaman/enhancement
In short, Shaman and Paladins are warriors, but every warrior isn't a Shaman or a Paladin.
Just like Tinkers are engineers, but every engineer isn't a Tinker.
Hope that helps.