New to Sitchin? -- Here are some helpful terms listed alphabetically:

Adamu
The first successfully genetically engineered Primitive Worker, The Adam.

Anu
Nibiru's ruler when the Anunnaki came to Earth; also, the planet Uranus

Anunnaki
"Those Who from Heaven to Earth Came." (From Nibiru to Earth)

Apsu
Primordial progenitor of the solar system, the Sun.

Bond Heaven-Earth
The complex instruments in Mission Control Center

Celestial Battle
The primordial collision between Nibiru and Tiamat

Celestial Time
Time measured by the processional shifts zodiacal constellations.

Deluge
The Great Flood.

Destiny
Predetermined course (of events, of orbit) that is unchangeable.

E.A.
"Whose home is water," the prototype Aquarius; first born son of Anu, half brother of Enlil; leader of the first group of Anunnaki to arrive on Earth; the fashioner of Mankind and its savior from the Deluge; given the Epithets Nudimmud, "the Fashioner"), Ptah ("the Developer" in Egypt), Enki ("Lord Earth"); father of Marduk

Eden
Location of the Anunnaki's first settlements, the biblical Eden, in southern Mesopotamia; later the area of Shumer

Enki
Ea's epthet- title after the division of duties and powers between him and his half brother and rival Enlil; father of Marduk by his spouse Damkina; failed to have a son by his half sister Ninmah, but fathered 5 other sons by concubines and also children by Earthling females.

Enlil
son of Anu and his sister- spouse Antu and thus the Foremost Son entitled to the succession to Nibiru's throne ahead of the firstborn Ea; military commander and administrator sent to Earth to organize wide-scale gold-obtainment operations; father of Ninurta by his half sister Ninmah, and of Nannar and Ishkur by his spouse Ninlil; opposed the fashioning of the Earthlings, sought Mankind's demise by Deluge; authorized the use of nuclear weapons against Marduk.

Gateway to heaven
The purpose of the launch tower built by Marduk in Babylon

Gilgamesh
King in Uruk; being a son of a goddess, went in search of immortality

Igigi
The 300 Anunnaki assigned to shuttlecraft and the way station on Mars; abducted female Earthlings as wives; frequent rebels.

Inanna
Daughter Nannar and Ningal, twin sister of Utu; was betrothed to Dumuzi; ferocious in war, lusty in lovemaking; mistress of Uruk and of the Third Region; known as Ishtar in Akkadian; associated with the planet we call Venus.

Ki
"Firm Ground," the planet Earth

Kingu
Tiamat's principal satellite; Earth's moon after the Celestial Battle.

Lulu
The genetically engineered hybrid, the Primitive Worker

Marduk
Firstborn son and legal heir of Enki and Damkina; worshipped as Ra in Egypt; jealous of his brothers, unsatisfied with Egypt alone as his domain, claimed and after exiles and wars attained supremacy on Earth from his city Babylon.

ME
Tiny object encoded with formulas for all aspects of science and civilization

Mission Control Center
In Nibru-ki (Nippur) before the Deluge, on Mount Moriah after the Deluge

Mount of Salvation
The peaks of Ararat, where the ark rested after the Deluge.

Nannar
Son of Enlil and Ninlil, the first Anunnaki leader to be born on Earth;patron god of Urim (Ur) and Harran; associated with the Moon; known as Sin in Akkadian; father of Utu and Inanna.

Nibiru
Home planet of the Anunnaki; its orbital period, a Shar, equals 3,600 Earth years; became the twelfth member of the solar system after the Celestial Battle.

Ningishzidda
Son of Enki, master of genetics and other sciences; called Tehuti (Thoth) in ancient Egypt; went with the followers to the Americas after he was deposed by his brother Marduk.

Ninurta
Enlil's Foremost son, mothered by Enlil's half sister Ninmah, and his legal successor; battled with Anzu, who seized the Tablets of Destinies, and with Marduk; found the alternative sources for gold and established alternative space facilities in the Americas; patron-god of Lagash

Nippur
Akkadian name of Nibru-ki, where the calendar of Earth years was begun in 3760 B.C.; birthplace of Ibru-Um (Abraham)

Shar
One orbital period of Nibiru around the Sun, equal to 3,600 Earth years.

Shumer
Land of the Watchers, the First Region of post-Diliuvial civilization; Sumer

Tablets of Destinies
Devices used in Mission Control Center to track and control orbits and trajectories; later on, a record of unalterable decisions

Tiamat
Primordial planet that broke up in the Celestial Battle, giving rise to the Asteroid Belt and to the Earth