Songs automatically moving to iTunes Media folder on mac

Hey guys, I recently transferred most of my music from the External HDD to my mac (around 80 gigs) and some of these files automatically went to the iTunes Media folder. I think it was due to changing the titles of the song, the artist, or album work but why does it do that? Why does it not just stay in the folder where I put the rest of my music? Is there a way to fix or just make my mac not do it?