Haloalkanes undergo nucleophilic substitution whereas haloarenes undergo electrophilic substitution. Account for it.

Haloalkanes undergo nucleophillic substitution reaction due to high electronegativity of the halogen atom, the C—X bond in haloalkanes (alkyl halides) is slightly polar, thereby the C-atom acquires a slight positive charge (≡ C^+δ—X–^δ). Hence, C-atom is a good target for attack by nucleophiles (electron easily rich species). Therefore, the X-atom of the halo-alkane is replaced by a nucleophile easily.
Nu : + R^+δ—X^δ → R—Nu + X^–
On the other hand, in haloarenes the halogen atom releases electron to the benzene nucleus relatively electron-rich with respect to halogen atom. As a result, the electrophile attacks at ortho and para position. Hence, haloarenes undergo electrophilic substitution reactions.