Shadow Clone Technique is quite similar to that of the Clone Technique, this technique allows the user to create exact clones of the user, but these clones are solid and real copies, not illusions. The clones are capable of performing techniques on their own, they can even bleed and die, but will usually explode or rather disperse after one or two solid blows or they can disperse on their own. The clones have the exact same physical conditions as the user, which would mean if the user is injured the clones produced would be injured as well.
Since the user's chakra is almost evenly distributed among every clone, making them nearly identical with the user as they have equal fraction of chakra imbued in them they cannot be distinguished, even by the use of ocular powers, such as Byakugan and Sharingan.