If you have heard contemporary music and have not understood anything, you can play one game. The rules are simple: tell your friend about what you heard without naming the style, composer, or title of the piece.
You ask, but how to tell, I didn’t understand anything?
Start with a rough composition of the instruments or describe what the noises and sounds were like. Describe whether the accords were harsh or soft, pleasant or disturbing. What was this music like, what associations did it evoke? What would happen in a movie if this kind of music was played off-screen?
You don’t need professional training to talk about it. Let your heart let the music into you and tell it all yourself. Before you have time to look around, everything will become clear and simple.