The address of the front door of my office using the app what3words is ///:headed.rating.locate which refers not just to my street address of 1756 Gilpin Street, Denver, Colorado 80218, but to the actual three meter by three meter box location within that parcel of real estate where the front door of the building is located.
The app makers assigned every single three meter by three meter square in the world an address consisting of three English words. This is a precision roughly equivalent to a GPS coordinate with degrees, minutes, seconds and tenths of seconds of latitude and longitude, which is especially useful for large industrial, academic or medical campuses, parks or open space, and large buildings. In some circumstances, you would also need to know the floor of the multi-story building in question.
This is also roughly the precision of GPS systems that have been scrambled for civilian purposes, and is about the accuracy of GPS guided artillery, guided missiles and smart bombs.
The use of English words is desirable because people remember words better (and can communicate them orally better) than they can remember GPS coordinates and communicate them orally, a key insight into how a user interface should work. The what3words address of my office, despite being more specific, is probably easier to remember or take down over the phone, than even the full street address, although the what3words address can't be applied on the ground without the app.
The app translates the words into GPS locations using a key. More obscure words are used to describe less high interest locations like locations in the middle of an Antarctic or Arctic ice fields, oceans and deserts. More common words are used to describe locations in highly populated areas that are developed enough to be likely to have lots of users (as of the time that the name were assigned on a permanent basis a few years ago).