Block from U+2FF0 to U+2FFF. This block was introduced in Unicode version 3.0 (1999). It contains 16 codepoints.
The Wikipedia provides the following information on block Ideographic Description Characters:
Ideographic Description Characters is a Unicode block containing graphic characters used for describing CJK ideographs. They are used in Ideographic Description Sequences (IDS) to provide a description of an ideograph, in terms of what other ideographs make it up and how they are laid out relative to one another. An IDS provides the reader with a description of an ideograph that cannot be represented properly, usually because it is not encoded in Unicode; rendering systems are not intended to automatically compose the pieces into a complete ideograph, and the descriptions are not standardized.