What is the meaning of -나?

An interrogative marker in the familiar speech level; with (-yo), also used in the polite speech level.

Conveys a question addressed to oneself.

In the plain speech level, an interrogative marker denoting polar (yes-or-no) questions.

Used in 나 보다 (-na boda).

Post-vowel allomorphic form of 이나 (-ina).

Post-vowel and post-liquid allomorphic form of 으나 (-euna).

Source: wiktionary.org