deb-src http://http.debian.or.jp/debian stable main contrib non-free
deb-src: 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/source/Sources.gz http://http.debian.or.jp/debian/dists/stable/main/source/Release http://http.debian.or.jp/debian/dists/stable/contrib/source/Sources.gz http://http.debian.or.jp/debian/dists/stable/contrib/source/Release http://http.debian.or.jp/debian/dists/stable/non-free/source/Sources.gz http://http.debian.or.jp/debian/dists/stable/non-free/source/Release