Moving Average Convergence Divergence (MACD) is a momentum indicator that relies on moving averages to calculate the strength of price trends.
On top of that, the MACD is best known for giving out potentially accurate buy/sell signals as follows :
When the MACD line crosses Above
the signal line (lower half of the histogram) = Buy signal
When the MACD line crosses Below
the signal line (upper half of the histogram) = Sell signal