Linked from
The 19 pages that link to Brillouin zone, each with the reason it gives.
Band gapRelated: Band extrema are located at points in this zone.
PhononRelated: Phonon wavevectors are commonly represented within this reciprocal-space region.
Bravais latticeBroader topic: It packages reciprocal-space translations into a fundamental region.
Fermi surfaceRelated: Fermi surfaces are commonly mapped within this momentum-space cell.
Bloch's theoremRelated: Bloch wavevectors need only be considered within one reciprocal-space cell.
Band structureRelated: Band energies are plotted across this reciprocal-space region.
Electronic band structureRelated: Band energies are plotted across this reciprocal-space region.