Succulents have a natural wax coating on their leaves that can sometimes look white and powdery. This coating both seals in water to reduce loss from evapotranspiration and helps reduce sunburn. A succulent grown in direct sun can develop a thicker coat of epicuticular wax, aka farina.
The farina is easily brushed off by hands, packing materials, neem oil, and others leaves. This is rarely harmful to the plant, but it does leave bare patches. Old farina will not usually grow back, but new leaves with full coverage will eventually replace the old, marked leaves. For particularly powdery varieties, such as Dudleya, Echeveria cante, and Echeveria laui, limit handling the leaves as much as possible. Also try to water the soil directly to avoid getting droplets on the leaves.