What's a GBAO permit?

What's mean GBAO and how to get a permit to visit the GBAO?

GBAO (Kuhistoni Badakhshon Autonomous Province of Tajikistan) is the frontier territory of Tajikistan and has special permission entry, which allows applicants to visit Khorugh, Darvoz, Vanj, Rushon, Ishkoshim and Murghob districts. Foreign citizens can obtain GBAO with the e-visa application. www.evisa.tj