According to Sri Vaishnava Agamas, Vishnu has five aspects or
modes. They are para, vyuha, vibhava, antaryami and archavatara. Bhagavan Vishnu is
said to assume various manifestations from time to time to protect the
virtuous, punish the wicked and re-establish dharma. These incarnations are
called vibhavas, more popularly avatars or descents into the world.
The popular and well known Vibhavas are ten in number –
Matsya, Kurma, Varaha, Narasimha, Vamana, Parashurama, Rama, Balarama, Sri
Krishna and Kalki.
Another set of popular Vibhava form is 24 in number. This includes
various Sages and other minor incarnations like Mohini Avatar etc.
When a devotee following dharma is danger, Vishnu appears in
human or non-human or inanimate form to help the devotee. These forms are also
part of Vibhava.
Vibhava is the form that Vishnu takes to help a living being
in the universe.