Halfwidth and fullwidth forms
Halfwidth and Fullwidth Forms is the name of Unicode block U+FF00–FFEF.
U+FF01–FF5E reproduce the characters of ASCII 01 to 7E as fullwidth forms (zenkaku), that is, as monospace glyphs with the same width as a fullwidth Kanji. This is useful for typesetting Latin characters in a CJK environment. U+FF00 does not correspond to a fullwith ASCII 20 (space character), since that role is already fulfilled by U+3000 "ideographic space" ([[ ]]).
U+FF65–FFDC encode halfwidth forms (hankaku), of Katakana and Hangul characters. U+FFE0–FFEE are fullwidth and halfwidth symbols.