It's the region where you live!!
FCC Version (United States)
United States: The FCC version complies with the Federal Communications Commission regulations. It usually allows higher transmission power, resulting in better range.Usage domain: legal in the U.S., often not compliant in other countries.
LBT Version (Listen Before Talk)
Europe (including the European Union) – LBT is required to comply with ETSI regulations, especially under the Radio Equipment Directive.
Japan, South Korea, Australia – LBT is mandatory for certain frequency bands.
Latvia and Russia – LBT usage documented, for example in RFID systems.