What is "z-variant"

n. ''(Unicode)'' a shape variant of a Han character, encoded for historical reasons.

In Unicode, two glyphs are said to be Z-variants (often spelled zVariants) if they share the same etymology but have slightly different appearances and different Unicode codepoints. For example, the Unicode characters U+8AAA 說 and U+8AAC 説 are Z-variants. The notion of Z-variance is only applicable to the “ CJKV scripts” — Chinese, Japanese, Korean and Vietnamese — and is a subtopic of Han unification.