Yagna As A Sacrifice
Agni - The Aryan God of Fire was looked upon as the protector of men and their homes. Agni was propitiated to spell prosperity for the Ayran tribe. The central fireplace where Agni was lit and preserved by the Agni-hotras "preservers of fire" was the common hearth of the Aryan tribe, originally. Later on it came to be ritualised as the Yagna - fire sacrifice.
Yagna is a term we normally hear in today's society. It is popularly understood as a fire sacrifice involving the offering of grains, clarified butter, sandalwood etc, to a fire . This fire is ignited in a special fireplace called the Kund, which literally means a "Pot". Yagna is normally performed with the objective of ushering in prosperity or to avoid disaster. For performing a Yagna a minimum number of five priests are required although many more priests may participate. A Yagna is normally accompanied by mass feeding of people, the food being distributed as Prasad (i.e food which has been sanctified by offering it to the Gods). Rituals similar to yagna are performed during marriage, thread ceremony, vaastu shanti (opening ceremony for a house), etc. when a homa or sacred fire is ignited in a kund.
It is widely known that Yagna is a very old tradition in the Hindu religion and it is looked upon as a Vedic ritual. In Vedic literature there are innumerable descriptions of a Yagnas being performed. The origin of the Yagna though lost in history, the rituals associated with it today throw light as to its nature.