An abacus is a calculating tool that uses movable beads on rods or wires to help people add, subtract, multiply, and divide. Each rod represents a different place value: ones, tens, hundreds, and so on. By sliding beads up and down, you can represent numbers and perform calculations quickly.

The abacus was invented thousands of years ago and became one of humanity's most important tools for mathematics and commerce. Before calculators and computers, merchants used an abacus to total purchases, bankers used one to track money, and students learned arithmetic with them. The ancient Romans carried portable versions for business. In Japan, the soroban (a Japanese style of abacus) is still taught in schools because it helps students understand how numbers work and can be incredibly fast once you master it.

Different cultures developed their own versions: the Chinese suanpan has more beads per rod than the Japanese soroban, while the Russian schoty has a completely different design. Some people who've trained extensively with an abacus can eventually do calculations in their head by visualizing the beads moving, performing mental math faster than most people can with a calculator. The abacus proves that you don't need electricity or screens to do sophisticated mathematics, just a clever system and practice.