Trying Harmonics

Hi guys! I just discovered some new tools and had to try them out. I've seen them on some of Mustermanns Posts and found them intriguing, here's what they look like on my charts. 

Here's what I think how it works:

• There's 5 points that are connected in the chart
• They, more or less have the same time passage
• A Fibonacci Retracement is drawn from Point A to Point D (I got the values from one of Mustermanns posts)

What I haven't understood yet is what they mean or how they help me. Why the Fibonacci? And how do I combine them with other strategies or what should I focus on with Harmonic Patterns?

Have a great day :)