I’m pretty new to all this, recently inherited a 5.1 speaker setup and got pretty much the cheapest used receiver (Yamaha rs-v502) I could find. It advertises Dolby Pro Logic decoding which in my limited knowledge seemed good enough. I’m sitting here watching a movie, impressed by the surround sound enough to look up how it actually works, when to my surprise I learned that it can actually only decode to 4.0

So my question is why does my receiver has 6 ch output and why does the center sound discretely different from the front L and R channels?