The horse was unknown in South America before the Spanish arrived, so heavy loads were typically carried either by porters or by llamas. The maximum load that a llama can safely carry is probably on the order of 30-50kg (65-110lb), depending on the size of the animal. Pack horses and mules, for comparison, can typically carry 60-90kg (130-200lb). Llamas are not generally suitable as riding animals. They are, however, extremely sure-footed, which fits them perfectly for the steep and narrow mountain trails of the Andes, allowing them to travel over terrain where horses can not go.
The use of llamas is reflected in the design of Inca roads. Roads made for horses typically follow valley floors and must ascend and descend in long, winding arcs, as horses and even mules have difficulty with steep gradients. Inca roads are often built high up on mountain walls and ridges, and even feature flights of steps: impassable for horses, but not for llamas or men.
In addition to serving as pack animals, llamas also provided clothing (their wool, while coarser than that of the related vicuña, is suitable for spinning), meat, and fuel (dried llama dung was used for cooking fires).
Llamas are camelids, which means that they are distant relatives of camels. Other South American camelids related to llamas include alpacas, vicuñas and guanacos.