The spy glass on the right side (depends on skin) toggles the filter panel view. The drop down button shows the filter options menu. The cross clears the filter. The three buttons at the left are the most common attribute types to filter on (artist, album, song) the other attribute types are selected from the filter options menu:

The filter options menu contains the following settings and functions:

• Filter on "attribute type"
• Contains Text
• Starts With Text
• Matches Text 
• Filter Track Based
• Clear Filter
• Show On-Screen Keyboard

At the General 2 page of the preferences screen there are additional settings for the filter. One of that settings is the automatic update of the results. When that option is set, the filter results are automatically updated after each keystroke. There are minimal 3 characters necessary before automatic filtering takes place. When this feature is disabled, the Enter key should be pressed to update the filter results.

The filter results are shown in the album grid area. The results can either be albums or tracks. Partly depending on the selected attribute type Filter on "attribute type", but also on the Filter Track Based setting. For instance you when you search for artists, you can either search for the albums of an artist or for all tracks of that artist. Last option will also show the collection albums containg tracks of an artist.

Album results shows resulting covers.

Track results shows resulting tracks.

When track results are shown, also buttons are shown below the results to easily play tracks or add tracks to the playlist.

The buttons have the following functions:

Headers
This toggles the album headers on or off. Note that when clicking on the cover in the header, the album info panel (booklet) is opened for the album.

Add
This adds the selected tracks to the playlist. For more info see Add tracks of the manage playlist chapter.

Play
This (optinally) adds the selected tracks to the playlist and plays the track immediatly. For more info see Play tracks of the manage playlist chapter.

Play Next
This (optinally) adds the selected tracks to the playlist and plays the track after the current playing track is finished. For more info see Play tracks as next of the manage playlist chapter.

Deselect
Deselects currently selected tracks.