The standard grips this chord is usually shown with.
Fm is F, Ab and C, a minor triad. The shape this page opens on is written 133111, lowest string first.

Also written Fmin, F- or F minor. The same chord either way; which spelling you meet depends on who wrote the chart.
There are 9 common shapes for Fm on the guitar, and 47 derived voicings in the triad family.
In which keys. Every note of Fm belongs to C minor (the iv), C# major (the iii), Eb major (the ii), F minor (the i), Ab major (the vi) and Bb minor (the v).
The common shapes, written lowest string first: 133111, xx3111, xx3564, xx6564, x8656x, x-8-10-10-9-8, x-11-10-10-9-x, 13-11-10-10-x-13, 13-15-15-13-13-13.
Triad. Three notes across one string set. Fm has xx311x, xxx111, x331xx, xx3111, 1331xx, x3311x, 433xxx, 4335xx.
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.