The combination of one s and two $\mathrm{p}-$orbitals to form three hybrid orbitals of equal energy is known as ${\mathrm{sp}}^2$ hybridization 

These ${\mathrm{sp}}^2$ hybridized orbitals are oriented at an angle of ${120}^{°}$

So the structure of ${\mathrm{BF}}_3$ molecule is 

But in case on ${{\mathrm{NO}}_2}^{-}$ nitrogen molecule contains a single lone pair and double bond

So it is also ${\mathrm{sp}}^2$ hybridised