They're the Pride Lands' termite experts.
The aardwolf is a four-legged species of moderate size. Its face is generally narrow and pointed, and it has large bat-like ears, a long snout, and wide eyes. Most aardwolves have pelts of varying shades of gray, some of which carry tints of blue or purple. Their fur is darker in places, most notably on their faces and paws, and on their stripes, which can be found on their backs, chests, face rims, legs, and necks. Their underbellies are lighter than their primary fur color, and their manes are black. Some aardwolves have manes that extend above the head and form tufts. Their inner ears are pink, and they have wide yellow sclerae. Overall, aardwolves bear a striking resemblance to hyenas, which they are often mistaken for.
Aardwolves are reserved, shy creatures that only emerge at night to feed on termites. They are essential to keeping the termite population in check in the Pride Lands, despite rarely being seen. Aardwolves tend to roam from place to place, preferring the shelter of empty aardvark dens for sleep.
One night, while scrounging around the aardvark dens, a pack of aardwolves is mistaken for hyenas. Kion warns the supposed hyenas to leave the Pride Lands for good and uses the Roar of the Elders to banish them to the Outlands. In the wake of Kion's fury, the aardwolves flee in terror and abandon their duties as termite-eaters in the Pride Lands.
Without the aardwolves, the Pride Lands become overrun with termites, and Kion brings the problem before his father, Simba, who suggests that he bring the matter up with the aardwolves. Kion realizes that he had accidentally banished the aardwolves instead of the hyenas, and he resolves to bring them back to the Pride Lands in order to alleviate the termite problem.