iTunes stores your music 2x?

I have a question, say you downloaded new music to your computer in a folder called New Music, than you upload them to your iTunes through "add to library" to listen to the music on iTunes, does iTunes put those files also in another folder in 'music->iTunes' which in turn creates a duplicate?

I ask because I'm wondering if I download music, after i upload them to my iTunes should I delete that downloaded file because iTunes created a duplicate so that 3mb song doesn't turn in 6 mb due to 2 copies?

I noticed in my iTunes folder i have that song as well as the original folder after i upload them to iTunes so can i delete the original file?

so if i uncheck that, can i delete the files in the iTunes folder?