Changeling or Shapeshifter was a term used for those species, such as the Shi'ido or the Clawdites, with the ability to change their appearance or shape.[1]
Because of the mistrust some beings had of shapeshifters, they would often try to hide their species of origin.[2] Others were valued as assassins, spies, and observers.[1]
Some beings were also able to transform through the Force by using the reflections the life forces around them. Those species included the Force wielders.[3]