Yaksha is the name of a divine group . The lord of the direction of North, Kubera is their chief. Many puranas mentioned Yakshas as follwers of Indra in his wars against the demons. In ahaabhaaratham too, this race is mentioned many times. Yama stood before Yudhishthira in the form of a yaksha while testing him in the forest.
The often mentioned demi-god groups are Rudras,Maruths, Aadithyas, Vasus, Siddhas, Saadhyas, Gandharvas, Garudas, Nagas, Kinnaras, Kimpurushas, Vidyaadharas, Yakshas or Guhyakas etc. Some groups have a fixed number of entities in them. For example, Rudras are eleven in number, Aadithyas are twelve, Maruths are seven and the like.