( The first N in this name is pronounced like n in 'no', the Y like Y in 'you' and the last N like N in 'turn'.)
Naaraayana is a divine sage , a close friend of another divine sage Naaraayana. Arjuna and Krishna were incarnations of Nara and Naaraayana respectively. Hence the frequent reference to them as Nara and Naaraayana in the epic.
Nara and Naaraayana moved together. Both protected gods from the demons. Nara wielded a bow and Naaraayana, a discus. Both were known for their tremondous power of their terrible penances. there wee many stories illustrating their power and prowess. Eg, Dambhodhbhava's story, Oorvashi's story, war with demons on the ocasion of sharing of nectar between gods and demons etc.
Mahaabhaagavatham vividly describes their greatness.Both Nara and Naaraayana were treated as another form of Vishnu.