[i = Impressive knowledge pearl ]

• [i] the “H” in cnH initially referred to Hongkong
• For many years until 2010, China government constrained the onshore USD/cnY within a narrow range, essentially pegged. Nowadays the range is wider but still more controlled than the offshore version.
• [i] in 2010 cnH was officially launched under the auspices of PBOC and HKMA. I would say, that at that juncture, FX trading in USD/cnH switched from underground, unofficial to official.
• Compared to cnY, the cnH is traded in offshore markets (HK/SG/LDN….), is more market-driven, less controlled (by government). Greater volatility is seen in cnH.
• The offshore USD/cnH rate is almost always slightly higher than the onshore USD/cnY, but the spread is usually within 1%

Like all central banks, PBOC can and do influence the strength of cnY in popular paris like USD/cnY, EUR/cnY. I think PBOC has an easier job of influencing its own currency than other central banks do, thanks to capital control in China. PBOC can also influence the offshre cnH but by design cnH is less controlled.