They are generated by measuring the standard deviation of a return series over a rolling lookback window, then comparing that rolling value to a long-term baseline standard deviation calculated from several years of the same return series. The long-term baseline represents the market's "normal" volatility over a full cycle. The ratio of the rolling SDEV to the baseline is what defines the regime.
Regime state describes whether the market is behaving with more or less volatility than its long-term average. A ratio above 1 means the market is currently printing larger-than-normal moves — an elevated regime. A ratio below 1 means moves are smaller than normal — a compressed regime. It does not predict direction; it describes the character and intensity of price movement.
Regime state informs position sizing, stop placement, and strategy selection. In an elevated regime, stops are better served wider to accommodate larger moves and size should be reduced accordingly. Trend Continuation can provide larger more extended moves. In a compressed regime, the market tends to mean-revert and range, making breakout and trend strategies less reliable.
Regime is also used as a filter — many strategies are implicitly calibrated to a specific volatility environment, and applying them outside that environment is a common cause of live performance diverging from backtest results. Knowing the regime before taking a trade helps ensure the strategy being used is appropriate for current conditions and that the risk suites the environment.