The standard grips this chord is usually shown with.
Ab is Ab, C and Eb, a major triad. The shape this page opens on is written 431114, lowest string first.

Also written Abmaj, AbM or Ab major. The same chord either way; which spelling you meet depends on who wrote the chart.
There are 6 common shapes for Ab on the guitar, and 45 derived voicings in the triad family.
In which keys. Every note of Ab belongs to C minor (the ♭VI), C# major (the V), Eb major (the IV), F minor (the ♭III), Ab major (the I) and Bb minor (the ♭VII).
The common shapes, written lowest string first: 431114, xx1114, 466544, xx6898, x-11-10-8-9-8, x-11-13-13-13-11.
Triad. Three notes across one string set. Ab has x311xx, xx111x, x3111x, xx654x, xxx544, xx6544, 4665xx, x6654x.
The common shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.