Walking is the general action of moving a body. It is the most common form of transportation, involving the use of the legs to move from one spot to another. Species that walk are usually bipedal (ex. humans and anthros) or quadrupedal (ex. ferals). Images that display walking usually show one leg in front of the other, possibly with one foot in the air. Images that show both legs next to each other in contact with the ground should be tagged as standing.