FCC vs. FCCHD...same or different?

What is the difference between FCC & FCCHD? Are they owned by the same company? Can I use an FCC account in FCCHD?

Both services are under FreeConferenceCall, FCCHD is an older service with less features, it’s audio only, has 2 access codes, 1 for host, 1 for participants, no host pin, no paid upgrades available. It has it’s own mobile app to connect via internet, but again, audio only.