Difference Between the Two Delete Keys

I am brand new to the Mac ecosystem. Having loved my iPhones for the past two years, I have been wanting more Apple. So this past Friday, I purchased the Mac mini. Thus far, I love it, but there is a lot to learn since I have been living in Windows/Microsoft my entire life.

I am currently in the process of exploring and setting up my Mac mini, and, for some reason, iTunes decided to duplicate portions of my library. I'm not sure why, as there is no rhyme or reason to the particular files that were duplicated; either way, I think I have that issue under control.

However, when I tried to delete some of the duplicate files from the directory with the delete keys, nothing happened. With some research, I discovered that Command-delete was the necessary keystroke. It still did not work because I was trying to use the delete key next to the end key; I then tried the 'backspace' delete key, and that did the trick. So, I am wondering what the difference is between these two seemingly identical keys.