| A shell chord is a guitar term, mostly used in jazz, for a chord consisting of the root, 3rd and 7th. When comping a song for the first time, a jazz guitarist will often play shell chords instead of the more complex varieties, just to get the 'shell' of the song down before buckling down and finding what other chord voicings they can use.
In relation to learning chords, shell shapes can be a hindrance. Any set shape is a hindrance, actually. They keep you from thinking about what you're playing and why it works the way it does. Just sit down and learn your fretboard and intervallic theory. The rest will come naturally when you sit down with charts and practice. | 
