what3words is a system for identifying locations on the Earth's surface by a group of three words, each such combo corresponding to a 3-by-3 meter square. It is intended as an addressing system to replace such things as street addresses and latitude-and-longitude coordinates. Its system is proprietary, and they have used takedown notices in an attempt to squelch open-sourced reverse-engineered implementations of it, causing some flack. At least one such implementation is still currently online.
The algorithm uses a list of words and a hashing system where nearby points have totally different words connected with them.