The Percentage Price Oscillator (PPO) is a technical indicator used in financial markets to measure the difference between two moving averages as a percentage of the larger moving average. The PPO is similar to the Moving Average Convergence Divergence (MACD) indicator but uses percentages instead of absolute values. When the PPO line crosses above the signal line, it is considered a bullish signal, indicating that it may be a good time to buy. Conversely, when the PPO line crosses below the signal line, it is considered a bearish signal, indicating that it may be a good time to sell.