「足 (あし)」 means "foot" or "leg." This word refers to the lower limb of the body, used for standing and walking. It can refer to both the entire leg or just the foot. You use it when talking about walking or standing.

歩(ある)いたり立(た)ったりする部分(ぶぶん)です。足(あし)が長(なが)いです。