This indicator normalizes the MACD and RSI indicators to a range between -1.0 and 1.0 so they can be displayed together on the same chart to save screen real-estate.
While the MACD is a good indicator to detect trend changes, in some circumstances (such as a sideways range market) it can give false signals. The MACD is more likely to give a false signal when the RSI indicator is close to the centerline than if the RSI is signaling an overbought or oversold condition. Thus the RSI indicator and MACD indicator are commonly used together.
I have included a few features found in other MACD indicators that I have found helpful:
MACD line changes color if it is rising or falling
Dots at the MACD line to signal crossovers
The MACD signal line is hidden it by default as the information it contains is redundant. Hiding the signal line makes the indicator less busy.