Added on 28 September 2020
what3words has divided the world into 3x3 metre squares and allocated each square a unique three word identity. When installed on a mobile device, the what3words app automatically generates the relevant three words for the device's current location.
Most emergency services now accept what3words to enable a faster response.
Many other agencies, such as National Grid, Network Rail and the Environmental Agency, also use what3words to identify the location of incidents.
To find out how to use the app, read this what3words leaflet (pdf).
The what3words app is totally free, you can download it for OS or Android devices.