It is quite common to list metallicity for stars. For example for Teegarden's star, notable because one of its two planets (b) has an Earth similarity index of 0.95, the highest listed on the habitable-exoplanets-catalog, has a metallicity listed as -0.19±0.16 [Fe/H]. It would appear that the Fe/H estimator of metallicity is the most commonly used measurement, which makes sense in that most of the primordial matter was hydrogen (H) and the end product of a simple fusion cascade stops at iron (Fe) as iron has the [Sic, stable] isotope with the (Edit) least practicable binding energy available to fusion per nucleon of any element. But note comment by @johndoty and Once the chain of reactions reaches Fe, there is no reason to examine heavier or more stable nuclei, because the conditions are such that they are barely produced.
But what is -0.19 [Fe/H]? Perhaps the logarithm of the ratio of concentrations? And if so, where is sol in that regard and what range of [Fe/H] do we expect in what context? At the risk of seeming to ask multiple questions, all I am really asking for here is some simple explanation of metallicity so that when I see it cited I have some concept of what it means.