This property defines the Unicodes which belongs to Hangul Compatibility Jamo block
Characters like ㄱ,ㄲ,ㄳ, etc. are listed under Hangul Compatibility Jamo Block.
96 Characters are present in Hangul Compatibility Jamo Block starting with the Unicode point U+3131 that represents the character ㄱ.
Currently, as per latest version 15.0.0, Unicode supports 328 number of Block. Here are a few examples - Latin Extended E,Adlam,Aegean Numbers, etc.