Asura vivaha was marriage by purchase.
  In the paisacha form of marriage the bride was abducted in an unfair
  manner.
  Rakshasa vivaha was marriage by capture.
  Gandharva vivaha was love marriage.
    The four approved forms of vivahas were generally meant for members of
the first two varnas especially for the Brahmins. These four forms are
dharmya. According to Kautilya, the fact of their being dharmya signifies
that the patriarchal element is supreme in them and not in the unapproved
forms of marriage which requires the sanction of both the father and the
mother. Seemingly, the dharmya character of these marriages imposes upon
all varnas the obligation to observe them. But since the Brahmins and
Kshatriyas were charged with the responsibility of upholding the social order
(dharma), it is necessary that they should observe these approved forms of
marriage.
    The four unapproved forms of vivahas were generally meant for the three
lower varnas of Kshatriyas, Vaishya and Sudra. Within these, the rakshasa
and gandharva forms are permissible especially for the Kshatriyas.
    Asura vivaha is considered to be universal in ancient times. But it is
condemned by the Dharmasastras in strong terms, probably because of its
connection with the lower varnas.
    Paisacha vivaha is the worst of all marriages. Baudhayana prescribes it
for the Vaishyas and Sudras. Manu also corroborates it. These prescriptions
were probably intended to validate the marriage practices of those tribes who
were absorbed as two lower varnas in ancient society.
    The rakshasa form is prescribed by Manu for the Kshatriyas. But by the
third century BC it was no more approved even by the Kshatriyas.
    Gandharva vivaha, confined by some to only the Kshatriyas, was
probably followed by men and women of the other varnas as well. This can
be inferred from the rules laid down in the Dharmasastras as well as
numerous examples found in the general literary works.