A tang or shank is the back portion of the blade component of a tool where it extends into stock material or connects to a handle – as on a knife, sword, spear, arrowhead, chisel, file, coulter, pike, scythe, screwdriver, etc.
Many inexpensive knives and swords designed for decorative purposes incorporate partial tangs and are not intended to be used for cutting applications.
A full tang also increases the amount of stock metal in the handle of the tool which can be beneficial in altering the balance point of the tool since the blade of a knife or sword is often quite heavy compared to the handle.
Adding weight to the handle of a knife or sword to offset the weight of the blade moves the rotational balance point back toward the hand where it can be more easily manipulated to great effect, making for a nimble, agile tool.
In general, a forward-balanced blade excels at chopping but sacrifices agility and ease of manipulation; a centre or rear-balanced blade excels at agility but sacrifices raw chopping power.