Vaastu means site, foundation. On whichever land human beings etc live, that is all called Vaastu. It has remained in use since Rig Ved times. According to Rig Ved "Vaas" means "place to live" and the science dealing with it is called "Vaastu Kalaa", or "Vaastu Shaastra".

Vaastu is usually sued in Bangaal to signify homestead lands. All Vaastu lands, in fact all lands, are controlled by the Vaastu spirit - called Vaastu Purush, and the Vaastu Purush should be propitiated by Vaastu Yagya to live happily and safely.

Birth of the Presiding Deity of Foundation
Matsya Puraan says about the origin of Vaastu - Once the Daitya named Andhakaasur had a terrible fight with Shiv Jee. During this fight a few drops of sweat of Shiv Jee fell on the ground and from them was born a terrible creature who caused terror to the Universe. Once he advanced to kill Devtaa, but they caught him and buried him alive in the Earth. To pacify him they blessed him like thus - "You will be worshipped in all the pious rituals." and started living over him. That is how he got the name of "Vaastu Purush".

In "Vishwakarmaa Prakaash", Viahwakarmaa says that in mid-Tretaa Yug, a creature was born. He covered the Earth with his shadow and slept. Brahmaa brought him to existence on the 3rd day of Krishn Paksh of Bhaadrapad month, in Krittikaa constellation which fell on a Saturday. When this person was born, it was Vyatipaat Yog and Vishit Karn. Being born in mid-Bhaadrapad and during Kulik Yog, the man created a terror among all people. Seeing this Indra went to Brahmaa Jee. Brahmaa Jee said - "Do not worry, just pin him down on his face and you will be free from all fears." So the Devtaa pinned him down and sat over his entire body. Then Brahmaa Jee blessed him with the boon that he would be worshipped in all the sacred rituals, and those who will nor worship you, will face poverty, misfortune etc.

It has many divisions - house, temple, village, city, castle etc. There are many books on this matter - "Vaasturaaj Vallabh", "Samaraangan Sootradhaar", "Brihat Sanhitaa" (by Varaahmiri), "Shilp Ratn", "Grih Ratn Bhooshan", Hayasheersh Paanchraatra", "Kapil Paanchraatra" etc. Among Puraan, this topic is mentioned in Matsya Puraan, Agni Puraan, Bhavishya Puraan, and Vishnu Dharmottar Puraan.

According to Matsya Puraan there are 18 scholars in this area - (1) Bhrigu, (2) Atri,  (3) Vashishth, (4) Vishwakarmaa, (5) Maya Daanav, (6) Naarad, (7) Nagnjit, (8) Vishaalaaksh, (9) Purandar (Indra), (10) Brahmaa, (11) Kumaar (Kaarttikeya), (12) Nandish (Nandee), (13) Shaunak, (14) Garg, (15) Vaasudev, (16) Aniruddh, (17) Shukra, and (18) Brihaspati.

How to Worship Vaastu Dev
To worship Vaastu Devtaa, his idol or a Chakra (disc) is made. This Chakra is usually from 49 to 1,000 spokes. Various types of Chakra are drawn on various occasions and Devtaa are invoked in them and they are worshipped there. The Chakra with 64 and 81 spokes are especially popular. In these Chakra Indra etc 10 Dikpaal and Shikhee etc 45 Devtaa are worshipped and Kheer is offered to them. Vaastu Devtaa is worshipped in Vaastu Kalash and is prayed for peace and welfare.