iTunes is a free application for Mac and PC that allows users to organize and play digital music and video. It syncs content between computers and provides access to the iTunes Store. Some key milestones include selling over 70 million songs in its first year and over 10 billion songs total. iTunes holds a large share of the legal music download market in the US and was the second largest music seller behind Walmart in 2008. It is strongly integrated with Apple's iPod and the iTunes Store provides a significant revenue source, especially on Windows. However, some criticize its integration on Windows and difficulties exporting music from iTunes or downloading purchases again. Illegal music downloading and streaming services pose threats, but downloadable music and MP3 players remain
