Yagna is an ancient vedic ritual, where sacrifices are made to a particular divinity, using fire (Agni) as a medium. The words homam (havan), and yagna are used interchangeably today. However there is a difference between homam and yagna. Yagnas of ancient times generally involved an animal sacrifice, which could have been a cow, goat, horse, or buffalo. Yagna in its present form, where milk products (ghee or yogurt), fruits, flowers, cloth, and money are offered, is termed homam (in southern India) or havan (in northern India).

Brahmins and certain other castes receive a yagnopavitham at their Uppanayanam (coming of age ceremony). The yagnopavitham symbolizes the right of the individual to carry out yagnas or homams. However, even this principle has changed over time. These days at temples, only the brahmin priests (not the brahmin lay people, even if they have a yagnopavitham) can carry out homams/havans. At other temples, the homam is supervised by a brahmin priest, but lay people (brahmins and non-brahmins, men, women, and children) can all participate in the homam.

Yet another significance of the yagna is that prior to temple worship (being the norm as it is today among Hindus), the gap between lay people and gods was bridged by brahmins, with agni as the medium. The mode of temple worship is termed agamic, while communication to divinity through the fire god, Agni, is considered vedic. Temples of today are generally a combination of both vedic and agamic rituals.