The abacus is the most ancient calculating device known. It consists of a wooden frame, rods, and beads. Each rod represents a different place value—ones, tens, hundreds, thousands, and so on. Each bead represents a number, usually 1 or 5, and can be moved along the rods. Addition and subtraction can easily be performed by moving beads along the wires of the abacus.
In short it is a simple tool used for fast and accurate calculations. It helps develop right brain and overall intelligence. There are many other benefits, just to name few, it helps improve,
Mental calculation abilities & whole brain development