Add11 chords
A major triad with an eleventh added and no seventh underneath. The eleventh is the same note as the fourth an octave up, so it adds a gentle rub without the stronger pull of a sus4. Worship piano and modern pop use it as a slightly richer way to play a plain major chord.
Other chord types
MajorMinorDiminishedAugmentedSuspended 2ndSuspended 4thDominant 7thMajor 7thMinor 7thMajor 6thMinor 6thMinor Major 7thDiminished 7thHalf-Diminished 7thAugmented 7thAdd9Dominant 9thMajor 9thMinor 9th6/9Dominant 11thMinor 11thDominant 13thMajor 13thMinor 13th7sus47b57b97#9Dominant 7#11Minor 6/99sus4Power Chord (5)Minor Add97sus213sus4Minor Major 9thMajor 7#11Major 9#117b1313b913#117altAugmented Major 7thMinor 9b5Quartal (So What)