Hello, Chris.
From iTunes Help (6.0.1)
A display icon next to an item means the item is a video. Double-click the video to play it.
A book icon next to an item means the item is a PDF file. Double-click the file to open it in your default PDF viewer.
A moving zigzag next to a song means a song is being imported from a CD or your hard disk. A green checkmark means iTunes has finished importing the song.
An exclamation point next to a song means the song file can't be located. It may have been moved or deleted.
A broadcast icon next to a song means the song is stored on the Internet and is "streamed" to you when you click to play it.
A black checkmark next to a song means the song will be included in your next action. For example, only songs with black checkmarks are copied to your iPod or imported when you click the Import button. Or, when you're playing all the songs in a list, only the checked songs play.
A speaker next to a song means the song is currently playing. When importing a song you're also listening to, you see a moving zigzag instead of the speaker.
Chasing arrows next to a song mean the song is being copied or downloaded from the Internet.
If you see an arrow to the right of a playlist in your Source list, you can click it to publish your playlist on the iTunes Music Store.
If you see an arrow to the right of a song, album, or artist in your library or a playlist, you can click it to go to the page for that item on the iTunes Music Store. You can show or hide these arrows by selecting or deselecting the "Show links to Music Store" checkbox in the General pane of iTunes Preferences.
If you see an arrow to the right of a podcast, you can click it to go to the page for that podcast in the iTunes Music Store.
If you see an exclamation point to the right of a Smart Playlist, one of the conditions for this Smart Playlist is a playlist that is not available. Click the exclamation point to choose another playlist or remove the playlist that is no longer available.
An eject icon appears to the right of CDs or digital music players in the Source list. Click the eject icon to eject the CD or to remove the music player from the Source list.
A bullet next to a song in your iPod shuffle playlist indicates the song is not currently on your iPod shuffle. If the song is authorized to play on your computer and is saved in a format that can be played on your iPod shuffle (such as AAC, MP3, or WAV), the song will be copied to your iPod shuffle the next time you connect it (if there is enough space on your iPod shuffle). For more information, see the documentation that came with your iPod shuffle.
A blue dot next to a podcast episode means you haven't started listening to the episode. A blue dot next to a podcast means there is at least one episode of that podcast you haven't started listening to yet.