A currency peg is a policy where a country fixes its exchange rate to another currency (usually the US dollar) or a basket of currencies, rather than letting it float freely against the market. The central bank defends the peg by buying or selling its own currency and adjusting interest rates as needed.
Pegged currencies can trade with very low day-to-day volatility for long stretches, but they carry the risk of a sudden, sharp devaluation if the central bank can no longer defend the fixed rate.
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How to Check the Way a Currency Is Managed
The regime behind a currency is published, not inferred. The four primary sources that say how a rate is governed, what each one can and cannot tell you, and how to keep the answer from going stale.