Here's why:

* Electronegativity: Nitrogen (N) has an electronegativity of 3.04, while Bromine (Br) has an electronegativity of 2.96. The difference in electronegativity is not large enough to create an ionic bond.

* Sharing electrons: Both nitrogen and bromine need to gain electrons to achieve a stable octet configuration. They achieve this by sharing electrons, forming a covalent bond.

The specific type of covalent bond is polar covalent. This is because, although the electronegativity difference is small, it is not zero. This means the shared electrons spend slightly more time closer to the nitrogen atom, making the nitrogen slightly negative and the bromine slightly positive.