Encodes (lat, lon) as a short base-32 string by interleaving the bits of each coordinate (Z-order). Common prefix length ≈ proximity, so adjacent points usually share long prefixes — handy for range queries on a B-tree or KV store.
Key formulas
Bits used for n-char geohash: 5n
Precision (cell side length) shrinks by factor 2 every extra bit; halves alternately in lat / lon.
Distance bound: d≤2⋅cell diagonal for same-prefix cells.