Wikipedia
In the fictional universe of J. R. R. Tolkien, Calaquendi means in Quenya "Light-folk", but was often translated "Elves of the Light". This name has a long history.
There existed two old elvish compounds in the Quenderin language, Primitive Quendian with *kwendī " Elves": *kala-kwendī and *mori-kwendī, meaning the "Light-folk" and the "Dark-folk". These two words date from the time before the Sundering of the Elves, or rather to the time of the debate among them about the invitation by the Valar to migrate to Valinor.
Both words were made by the party favourable to the Vala Oromë, and referred originally to Elves who desired the Light of Valinor versus Elves who did not wish to leave Middle-earth. *Mori-kwendī had from the beginning a negative sense, implying that these Elves were not so much opposed to the shadows Melkor had put upon Middle-earth.
The Quenya forms became Calaquendi and Moriquendi. The term Calaquendi in Quenya applied only to the Elves who actually lived (or had lived) in Eldamar; and the Moriquendi included all other Elves, whether or not they had participated in the March to Valinor. The Moriquendi were regarded as greatly inferior by the Calaquendi, who lived in the Light of the Two Trees, and had also received great knowledge and powers by living with the Valar and Maiar.
In Exilic Quenya the Noldor did not make much use of the terms Calaquendi or Moriquendi, which were rather offensive to the Sindar of Beleriand. Calaquendi became obsolete, and was used only in writings in the Parmaquesta.
According to The Silmarillion, Elu Thingol was not counted among the Moriquendi, although he was king of the Moriquendi of Beleriand; for he had seen the light of the Trees in Valinor.