Vastu Shastra -
Vastu Shastra are the textual part of Vastu Vidya - the broader knowledge about architecture and design theories from ancient India. Vastu Vidya knowledge is a collection of ideas and concepts, with or without the support of layout diagrams, that are not rigid. Rather, these ideas and concepts are models for the organisation of space and form within a building or collection of buildings, based on their functions in relation to each other, their usage and the overall fabric of the Vastu. Ancient Vastu Shastra principles include those for the design of Mandir (Hindu temples), and the principles for the design and layout of houses, towns, cities, gardens, roads, water works, shops and other public areas.
Havan is a fire ritual performed usually on special occasions by a Hindu priest for a homeowner ("grihasth": one possessing a home). The grihasth keeps different kinds of fire including one to cook food, heat his home, amongst other uses; therefore, a Yagya offering is made directly into the fire A homa is sometimes called a "sacrifice ritual" because the fire destroys the offering, but a homa is more accurately a "votive ritual".
It is rooted in the Vedic religion, and was adopted in ancient times by Buddhism and Jainism. The practice spread from India to Central Asia, East Asia and Southeast Asia.Homa rituals remain an important part of many Hindu ceremonies, and variations of homa continue to be practiced in current-day Buddhism, particularly in parts of Tibet and Japan. It is also found in modern Jainism.
Puja or pooja -
Puja or pooja is a worship ritual performed by Hindus to offer devotional homage and prayer to one or more deities, to host and honour a guest, or to spiritually celebrate an event.It may honour or celebrate the presence of special guest(s), or their memories after they die. The word "Puja" is Sanskrit, and means reverence, honour, homage, adoration and worship. Puja, the loving offering of light, flowers, and water or food to the divine, is the essential ritual of Hinduism. For the worshipper, the divine is visible in the image, and the divinity sees the worshipper. The interaction between human and deity, between human and guru, is called darshan, seeing.
Puja rituals are also held by Buddhists and Jains. In Hindu practice, puja is done on a variety of occasions, frequency and settings. It may include a daily puja done in the home, or occasional temple ceremonies and annual festivals. In other cases, puja is held to mark a few lifetime events such as birth of a baby or a wedding, or to begin a new venture