This property defines the Unicodes which belongs to Alphabetic Presentation Forms block
Characters like ff,fi,fl, etc. are listed under Alphabetic Presentation Forms Block.
65 Characters are present in Alphabetic Presentation Forms Block starting with the Unicode point U+FB00 that represents the character ff.
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.