Abmaj13 is Ab, C, Eb, G, Bb and F — with the thirteenth on top, and the eleventh left out.
It sounds full and wide open. Everything the major scale offers except the eleventh, which is left out because it fights the third.
Tonic — the major sound with most of the scale showing.
Also written AbM13, AbΔ13 or Ab major 13.

How you get to it. The turn that lands on Abmaj13 is to — the ii and the V of Ab — and shares its third and seventh with , so the hand barely moves between them.
Hear it land:→→
In which keys. Every note of Abmaj13 belongs to C minor (the ♭VI), Eb major (the IV, the subdominant), F minor (the ♭III) and Ab major (the I, the tonic).
Every note of Abmaj13 is in Ab major and Ab lydian.
Each of those is a page: the scale across the neck, and the chords it harmonises into — which is where Abmaj13 sits in it. Every scale.
Change one note of Abmaj13 and you have (drop the thirteenth), (the thirteenth becomes the eleventh), (drop the major seventh) or (the major seventh becomes the flat seventh).
Abmaj13 is a major chord — root, major third, fifth. Major chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.