The All Terrain Advance Raider (AT-AR), also known as the light AT-ST or simply scout walker, was one of the walkers used by the Galactic Empire during the Galactic Civil War.
Overall, All Terrain Advance Raider was quite similar to the AT-DP

AT-DP Ground Vehicle Vehicles

with which it shared the armored cockpit and central laser cannon. AT-AR had heavier armor than the AT-ST

AT-ST Ground Vehicle Vehicles

for frontline combat, but was also smaller and faster. Its "head" had an angular viewport, while a blister was located on either side of the walker's head. The cockpit sat one pilot

Imperial Combat Driver Organization Galactic Empire Military

and one gunner side-by-side.
A variant of the All Terrain Advance Raider, featuring additional weapons attached to its blisters and a body and legs resembling that of an AT-ST, saw service on Cilpar, while another had relatively thin armor and also went by the name light AT-ST.
A garrison on the jungle world of Jarnollen

Jarnollen Planet

had AT-AR walkers in their arsenal.