It won't play CDs or MP3s - for now. Sony surprised a lot of people when it said media server functionality would not be a part of the PS4. In short, that meant people couldn't stream their home videos or music through the system. Additionally, CD playback wasn't built into the machine, presumably because CDs aren't nearly as popular as they were eight years ago.
The outcry could prompt changes, though. Shuhei Yoshida, president of PlayStation Worldwide Studios, told GiantBomb the teams are already working on a possible fix, saying "the system guys are discussing how and when we can put these features on PS4."