Guóbiāo (国标) — literally “national standard” in Chinese (国 = national, 标 = standard). GB is a mandatory national standard (强制性国家标准); GB/T is a recommended voluntary national standard (推荐性国家标准), where T stands for tuījiàn (推荐 = recommended); and GB/Z is non-binding guiding technical document (指导性技术文件), where Z stands for zhǐdǎo (指导 = guiding).
GRE
Working Party on Lighting and Light-signalling Equipment (cf French: Groupe de Rapporteurs sur l’Eclairage)
LED
Light-Emitting Diode: A semiconductor device that emits light when energized by an electric current.