Em6 is a minor sixth chord made of 4 notes: E, G, B, C♯. It sounds bittersweet, a little mysterious, and you hear it in gypsy jazz, film music and minor-key endings. It is the i chord of E minor and turns up in 5 other keys.
The library above opens on Em6 with 14 shapes up and down the neck. Tap a shape to hear it, or play it one string at a time.