What are arsha marriages?

Marriage, amongst Hindus, is a religious sacrament. It is not merely for the fulfillment of sexual desire but a sacred bond, the purpose of which is to carry out the duties prescribed for men and women in family life.

Arsha marriage is one of the weight ways to perform a marriage recognized in the Dharma Shastra, the treatise on religious duty (dharma).

In this marriage the father of the bride i permitted to accept a cow and a bull from his son-in-law for facilitating the performance of sacrifices, which require the cow’s milk.

The form was named after the rishis (sages) because of the implicit sacrificial rites.
What are arsha marriages?