Cube mapping
A texture of six square faces wrapping a point, sampled with a direction vector instead of UV coordinates.
Ned Greene described environment mapping onto a cube in 1986. Six faces form a box around the sample point; a 3D direction vector picks the face and the texel, with hardware handling the seams. The obvious use is reflections — a shiny surface samples the cubemap along its reflection vector — and skyboxes, which are a cubemap drawn at infinity.
Beyond that, cube maps store omnidirectional point-light shadows and prefiltered environment lighting for PBR. Dynamic cubemaps re-render the scene six times from the reflecting point, so they're usually baked or captured by reflection probes.