What the chart shows
MACD is the difference between the fast EMA(12) and slow EMA(26) calculated from daily BTC closes. The signal line is an EMA(9) of MACD itself, while the histogram is the difference between MACD and the signal line.
How to interpret it
A MACD crossover above the signal line indicates strengthening upward momentum; a crossover below indicates weakening or downward momentum. Histogram direction helps reveal momentum changes, but MACD is lagging and is not a standalone buy or sell instruction.