The iPod application on the iPhone offers you dozens of ways to browse your audio and video files and play them. You can list your content by Playlist, Artist, Composer, Album, Song or Genre. There are also ways to view only Videos, Compilations and Audiobooks.
You can also turn your iPhone sideways to look at your music in Coverflow, the album-cover-clipping mode also used in iTunes and on iPods.
When the iPod is playing a song, you will get a screen with the album artwork and controls on the top and bottom.
At the bottom, you have a volume slider, a back, pause/play and forward button. Press the pause play button in the middle to pause the song.
At the top of the screen, you will see the name of the artist, song and album. You have buttons to take you back to the previous screen, or to an album song listing.
If you tap near the top of the screen you will get more controls: a repeat/loop button, a time scrub control, the current time into the track and time remaining, and a shuffle control. The time scrubber is particularly useful for moving to a section in a long podcast.