CJK Unified Ideographs Extension-A is a Unicode block containing rare Han ideographs submitted to the Ideographic Research Group between 1992 and 1998, plus ten ideographs added in Unicode 13.0 which had previously been mistakenly unified with others. The block has dozens of variation sequences defined for standardized variants. It also has thousands of ideographic variation sequences registered in the Unicode Ideographic Variation Database (IVD). These sequences specify the desired glyph variant for a given Unicode character. Wikipedia