This script defines a custom indicator called "Buy Signal Indicator." It calculates the 9-day Exponential Moving Average (EMA) using the ema() function. Then, it checks if the current candle closes above the 9 EMA and the preceding candle also closed above it with higher highs and higher lows. If these conditions are met, a green "BUY" label will be displayed below the candle. The 9 EMA line is also plotted on the chart for reference.