deb http://http.debian.or.jp/debian stable main contrib non-free
deb: とってくるものがなにか
http://http.debian.or.jp/debian: baseとなるURL
stable: どのdistsか
main contrib non-free: どのコンポーネントか
http://http.debian.or.jp/debian/dists/stable/main/binary-i386/Packages.gz http://http.debian.or.jp/debian/dists/stable/main/binary-i386/Release http://http.debian.or.jp/debian/dists/stable/contrib/binary-i386/Packages.gz http://http.debian.or.jp/debian/dists/stable/contrib/binary-i386/Release http://http.debian.or.jp/debian/dists/stable/non-free/binary-i386/Packages.gz http://http.debian.or.jp/debian/dists/stable/non-free/binary-i386/Release