The MACD indicator is a trendfollowing dynamic indicator which indicates the correlation between two Moving Averages of a price.
The Moving Average Convergence/Divergence  abbreviated as MACD  Technical Indicator is the difference between a 26period and 12period exponential moving averages (EMA). For showing clear opportunities, a
socalled signal line (9period moving average of the indicator) is plotted on the MACD chart.
The MACD is most effective in wideswinging markets. There exist three popular types for using the Moving Average
Convergence/Divergence: crossovers, overbought/oversold conditions and divergences.

Crossovers: A basic MACD trading rule is to open a put order if the MACD falls below its signal line. A call signal
occurs if the Moving Average Convergence/Divergence breaks above its signal line. It is also well known to open a call or put order if the MACD goes
above/below zero.

Overbought/Oversold Conditions: The MACD is also helpful as an overbought or oversold indicator. If the shorter moving average pulls away
dramatically from the longer moving average (e.g. the MACD rises), it is probable that the security price is overextending and will soon return to more realistic levels.

Divergence: An indication that an end to the actual trend may be near occurs if the MACD diverges from the security. A bullish
divergence occurs if the Moving Average Convergence/Divergence indicator is making new highs whilst prices fail to reach new highs. A bearish divergence occurs if the MACD is making
new lows whilst prices fail to reach new lows. Both of these divergences are most significant if they occur at relatively overbought and oversold Levels.
You can download the MACD indicator here: https://www.mql5.com/en/code/35
In the following video you can learn how to trade with the MACD indicator.